IMAGINE you're invited to the best party in the world, but then told you can only turn up for the final five minutes. Then to make matters worse, once you get there, you're thrown out almost immediately after you arrive.

That is the scenario that has unfolded for Johanna Jackson, the New Marske race walker whose time at the Olympics has not quite been the once-in-a-lifetime experience shared by so many other members of the Great Britain team.

For a start, she only arrived in London on Wednesday, with the Games almost finished and so many incredible stories already penned. Jackson's event, the women's 20km walk, was scheduled for the final weekend, and she was instructed to complete her training in the North-East rather than base herself in the capital for the opening ten days of action.

Still, at least when her event came around, she would have the chance to make history on the photogenic setting of the Mall, to soak up the support of an enthusiastic home crowd giddy in the wake of so much British success.

Sport doesn't always work like that though. So before Saturday's race had reached its halfway stage, Jackson was sitting disconsolate on the side of the pavement, disqualified after falling foul of the arcane rules of a sport that can look all but unfathomable to the untrained eye.

Having received two warnings for failing to keep at least one part of a foot in contact with the ground at all times, Jackson was shown a red card when she transgressed for a third time. In short, the judges felt she was running instead of walking. It had taken her so long to get here – this definitely wasn't the way it was supposed to end.

“I only came down to London on Wednesday,” said Jackson, who is a member of Redcar Race Walking Club. “I've waited so long to get here and was looking forward to racing so much, so for this to happen is just devastating.

“Unfortunately, disqualifications are the name of the game in race walking, they can happen. You can get disqualified, it's just this is obviously the worst place it could ever have happened. I don't think I did anything different to what I've done in all of my previous competitions.

“ It's been a really hard year. There were a lot of times when I thought I wouldn't even get to the Games because of injury, so I was really overwhelmed when I made it into the team. To come here and have that happen in front of my family and the home crowd is devastating. I feel like I've let everyone down because they wanted to see a show.”

Having settled herself into the middle of a 61-strong field, Jackson was picking her way through the pack steadily when she received her first warning at around the 6km mark.

Another quickly followed, but with a lifetime-best time in the offing, the 27-year-old was reluctant to hold back. She was in 30th position shortly before the 9km mark, but that would be her final involvement in the Games.

“I saw the judges throwing out some cautions, but while you take them on board, you still have to get on with your race,” said Jackson, who watched on disconsolately as Russia's Elena Lashmanova staged a grandstand finish to snatch gold. “They're warnings that you're close to the edge, but you have to push yourself in an Olympics and you don't really pay any attention until you see the cards.

“I didn't see the first card go up on the board, when I looked up I had two and I thought, 'Oh dear'. But I was on for a PB and was feeling great so I wanted to give it my all. There's no point pulling back just because you've got cards – you have to give it everything.”

The pain of disqualification clearly hurt though, and was exacerbated by the brevity of her previous experience of the Games.

“It's been a really surreal few weeks because I've been watching a lot of the Games, but not really feeling like I was part of it,” she said. “In the last couple of weeks, I've been thinking, 'Am I actually going to the Olympics after all?'

“I've just been watching it on TV like everybody else – I was sat at home watching the opening ceremony and everything. That's why I was really dying to get down here and get stuck in. I just still can't really believe it ended the way it did.”