The incident occurred when she stepped into the road during the opening stage holding a large cardboard sign with the words "Allez Opi-Omi!", meaning "Go grandpa-grandma", aimed at the television cameras as she stood with her back to the oncoming cyclists.

Germany’s Tony Martin was the first rider to fall, triggering a pile-up which left Spain’s Marc Soler with two broken arms and others with major injuries. At the time, Brian Cookson, the former International Cycling Union President, described the incident as "possibly the most stupid thing I have ever seen anyone do at a bike race".

The spectator, who fled the scene, was traced and charged with endangering lives and causing unintentional injuries. According to reports, the woman said in court that she felt "ashamed" by her actions and had made a mistake.

It would be good to think that such a calamitously foolish action would never be repeated. But you wouldn’t bet against it. Some time, somewhere, someone else watching a top-class sporting event will do something equally dumb.

Or maybe something worse. And knowingly.

For this high-profile case is merely the latest manifestation of something that has been a part of sporting events ever since they began – the influencing power of the spectator.

The spectator can ennoble an event, can generate emotions that make it reverberate with profound significance. The spectator adds noise, life, passion – a truth we have never seen more clearly than in the past 18 months of lockdown, where crowds have been subtracted from the equation.

The traditional role of the spectator is to support specific individuals or teams within a contest. Countless tributes have been made to the inspirational power of this largely vocal support.

Of course, this can work both ways, as – to remain within the realm of two wheels – France’s Julian Alaphilippe testified after retaining his men’s road race world title in Flanders last month.

After crossing the finishing line with a winning margin of more than half a minute, the Frenchman paid rueful tribute to the hostile reception he had encountered at many points of the run-in. "I really hurt myself in the final lap," said Alaphillipe. "There were also many Belgian supporters who wanted Wout van Aert to come back and it pushed me."

At the 2010 Commonwealth Games in Delhi, there were complaints from some visiting archers about partisan home support putting them off. One of the competitors most obviously affected was England’s 23-year-old Amy Oliver, whose six-out-of-ten score on her last effort in the final – amid a cacophony of local anticipation – was a significant contributory factor in the host nation moving past her team to win by one point.

"In Delhi, I think many of the crowd at the archery had probably never seen the sport before and some people were making a noise when archers were shooting, which is a bit like shouting when tennis players are serving," Oliver’s team-mate Alison Williamson told insidethegames.

"The spectators were very enthusiastic, and the message was soon relayed to them to please respect the archers. By the time I was in the individual competition it was a lot better. I think we all learned a lot from Delhi – particularly the younger members of the team. But you can’t guarantee silence at an event."

That was an example where inexperience, rather than malice, was the driving force. But there is malice aplenty in stands and stadia around the world. As one example of this inimical power, take this, from the autobiography of the former Manchester City and England forward Mike Summerbee - The Autobiography: The Story of a True City Legend.

On City’s first big European Cup away trip in 1968, after a goalless draw in their home leg against the then unheralded Turkish club Fenerbahce, the players experienced something new and unwelcome. Summerbee relates how, at 9am, on the day of the match, he went to his hotel desk to ask what the waves of noise were that he had woken up to, which he likened to the sounds of a plane.

He was told it was the noise of the Fenerbahce fans who were already in the stadium. By kick-off time, Summerbee observed: "I had never known such an intimidating atmosphere," Unnerved, and preyed upon by home players who knew their visitors could not risk retaliation for fear of causing a riot, City lost 2–1.

On that occasion the threat of spectators crossing the figurative, and actual, white line remained just that. But on so many other occasions that threat has turned into an injurious reality.

At one end of the scale, certainly in recent years, there has been the relatively harmless phenomenon of spectators running onto the field of play, clothed or – in the age of the streaker – unclothed.

The footage of the well-known Everton fan who evaded one police rugby tackle before falling to a second after running onto the Wembley turf during the 1966 FA Cup final has been seen countless times.

As have the images of those who have encroached into the magic circle either topless – in the bounteous case of Erica Roe, who ran onto the Twickenham pitch during a rugby union match between England and Australia in 1982 - or in the buff. In the latter case the iconic image of a naked man leaping over the stumps – and bails! – of the wicket during the 1975 Test match between England and Australia at Lord’s comes to mind…  

Unhappily incursions onto or into the field of play can be wittingly – or unwittingly, as in the case of the Tour de France onlooker – damaging.

Not surprisingly, the Tour de France’s perennial factors – high-speed riders and excitable crowds in narrow thoroughfares – produced perennial near-misses or incidents.

In 1994, a policeman stepped out to take a photograph around a corner, causing a crash that injured several riders. Five years later, Giuseppe Guerini crashed into a spectator standing in the middle of the road taking a picture. In 2006, Norwegian rider Thor Hushovd was cut by a green cardboard hand, given out by one of the sponsors, which was being waved by a spectator…

Sometimes other motives prompt the arrival in the sporting arena of those who should be on the other side of the barriers.

The long and involved nature of marathon running has made it vulnerable to illegal incursions. At the 1972 Munich Olympics Frank Shorter, who was born in Munich, became the first American in 64 years to win the Olympic marathon, having taken a lead he never remotely looked like losing after just 15 kilometres.

Shorter was not the first runner to enter the Olympic stadium, however, as a West German student had joined the course wearing a West German track uniform and run the last kilometre before completing a full lap of the stadium. Thinking that this was the winner, the crowd began cheering him before officials realised the hoax.

Shorter arrived 35 seconds later, as the interloper was being escorted off the track by security and was perplexed to see someone ahead of him - and to hear the booing and jeering.

Eight years later, another high-profile false finisher, Rosie Ruiz, was briefly hailed as the first woman home in the Boston marathon before it became clear she had joined it over the final mile.

Moving along the scale of potential harm – a spectator at the London 2012 Olympics threw a beer bottle onto the track behind Usain Bolt as he was on his blocks before the men’s 100 metres final. Thankfully Bolt, who went on to retain his title, was unaware of the incident.

More sinister attempts to put sporting performers off, particularly footballers, have involved lasers being targeted upon individuals from within the crowd. 

At the 2004 Athens Olympics, the men’s marathon endured a damaging incident as the leader, Brazil’s Vanderlei de Lima, was accosted by a spectator who rushed onto the course. De Lima eventually finished third but declined to appeal against the result. He gained an extra award when the International Olympic Committee subsequently gave him the De Coubertin medal.

Sometimes spectators have made themselves open to harm by exceeding the bounds of acceptable or sensible behaviour. In January this year, a spectator who entered the racetrack during the Wellington Cup in New Zealand almost got themselves trampled to death under the speeding horses.

Similarly, sometimes, the sporting world can bite back at those who literally or metaphorically cross the line. In 1989 the mercurial manager of Nottingham Forest, Brian Clough, hit numerous home fans who invaded the pitch in the wake of his side’s 5-2 win over Queen’s Park Rangers. While opinions differed on this approach, two of the young men involved arrived for a public kiss-and-make-up session with Clough a couple of days later.

On January 25 1995, a Crystal Palace fan ran down 11 rows of stairs to abuse Manchester United’s Eric Cantona, who had been sent off for kicking his marker, Richard Shaw. The spectator got a powerful response from the Frenchman, who launched a kung-fu style kick at him that was followed up by efforts to land several blows.

Cantona was banned for eight months.

This was an unusual inversion of the normal state of affairs in football when spectators start acting beyond the pale. In March 2019, Aston Villa and England's star midfielder Jack Grealish, now of Manchester City, was left sitting stunned on the turf in his team’s away Championship match against local rivals Birmingham City after a home supporter had run up behind him and punched him in the back of the head.

Both clubs expressed their repugnance at the action, with Villa commenting that a "red line has been crossed by this cowardly on-field assault". In a statement, Grealish said he was shocked and scared and felt lucky it wasn’t worse.

Let’s face it. It could have been. It often is…

In 1993, during a break between games at the Hamburg tournament, 19-year-old Serbian tennis player Monica Seles, who had won eight grand slam titles, was stabbed in the back by a home fan. According to police, the fan intended to injure Seles to enable Germany’s Steffi Graf to regain her world number one ranking.

Seles took only a few weeks to recover from her physical injury, but the effects of the attack had a long-term impact upon her and, although she added the 1996 Australian Open to her collection of Grand Slam titles, she struggled to reach the levels she had achieved as a teenager and she played her last professional match in 2003.

Spectator violence at sporting events has been chronicled with increasing thoroughness over the past 150 years.

On February 7, 1879, around 2,000 spectators in Sydney invaded the pitch during a cricket match between a visiting English team and the New South Wales Cricket Association. Two English players were assaulted and three fans arrested.

Many of the most egregious early instances took place within The Victorian League – since 1990, the Australian Football League - home of Australian Rules football.

On June 7, 1902 umpire Henry "Ivo" Crapp was assaulted by Carlton fans. Two years later, the same umpire was under attack again from a Carlton supporter who ran on and punched him in the face.

In 1909, when it was announced there would be no extra time after the Scottish Cup final replay between Celtic and Rangers had ended goalless, around 6,000 fans of both clubs fought a pitched battle on the Hampden Park field. Goals and fencing were destroyed and fires lit around the stadium. It took two hours to end the riot, by which time 60 spectators – and 58 police officers – had been injured.

In 1912, the notorious unloveable baseball player Ty Cobb, playing outfield for the Detroit Tigers against the New York Highlanders, ran into the stands and attacked a handicapped fan who had been heckling him. His reported reaction after being rebuked for this was, "I don’t care if he’s got no feet!"

A year later, one of the most shocking incidents to have taken place at a sporting event ended with Emily Davison being trampled and killed by King George V’s horse Anmer after she had entered the course during the 1913 Epsom Derby in order to make a protest on behalf of the suffragette movement seeking the vote and improved rights for women.

On February 13 1971, during the second day of the seventh and final Ashes Test between Australia and England at the Sydney Cricket Ground, beer bottles and cans were thrown onto the outfield and English fast bowler John Snow was loudly booed and manhandled by a drunk and drug-affected fan on the boundary shortly after Australian Terry Jenner had been forced to retire after ducking into a bouncer from Snow.

English captain Ray Illingworth led his team from the field in disgust, but England returned seven minutes later after umpires Tom Brooks and Lou Rowan had said failure to do so would have meant the Ashes being awarded to Australia. During a further seven-minute delay to clear the field, a sight-screen attendant was carried unconscious from the field after being hit by a beer can. A total of 14 fans were arrested for offensive behaviour and a further 190 were ejected.

Crowd violence took a fatal turn on December 6 1975 when one of a group of fans that invaded the pitch during a match between Israeli football teams Maccabi Rehovet and Kfar Gvirol stabbed and killed Maccabi player Moti Kind.

In an FA Cup sixth round match in 1985 between Luton Town and Millwall, visiting fans rioted and home fans responded in kind. The Luton goalkeeper was hit on the head by a missile and 81 people were injured, 31 of them police.

On February 1 2012, rioting between rival fans after a football match between Egyptian teams Al-Masry and Al-Ahly escalated to the point where 73 people died and at least 1000 were injured.

On June 30 2013, a football match in the Brazilian state of Maranhao saw the referee getting into an altercation with a player which ended with him fatally stabbing the player. Fans then attacked the referee and beat him to death.

In July 14 2013, at the Nabire Regency Boxing Championship in Indonesia, a riot following a defeat of one of the home-town boxers ended with a stampede that left 18 fans dead and 40 injured.

These are just some of the most fatal - and ultimately saddening - examples of what happens when fans venture onto the field of play.

Once spectators turn into actors in the sporting dramas they observe, the path is set for disruption at best and at worst – the worst. The Tour de France sign-bearer has put herself into a long, unhappy narrative of fan excesses which, sadly, will continue to develop for as long as people gather to watch sport.