How does a 28-year-old accounts clerk from south London get into such a fix? Easy - she saw The Motordrome Wall of Death's advertisement in the monthly motorcycle magazine Backstreet Heroes calling for "suitable female victims who feel brave enough to ride the wall" to come forward. Stunt riders Allan J Ford and his partner, Ned Kelly, are hoping the ad will end their search for a "tank rider" to renew the long-lost tradition of female stunt riders in the show.
The ideal girl according to Ned, who has broken his collarbone and ribs and most of his fingers in eight years of wall-riding, is "familiar with motorcycles and confident with a crowd, but above all both light and pretty".
As many as 11 leather-clad hopefuls turn up for the audition under the imposing glare of the Battersea Power Station. Among them is Lucy Elliott, 20, who has only just passed her motorcycle proficiency test, but as her mother says, "eats, breathes and sleeps bikes". Mrs Elliott has come to support her daughter - what else can a responsible caring parent do? "I wouldn't dare stop her from doing it," she says - "she'd be so upset it would be ridiculous." After a hair-raising spin on the front of the bike there is indeed a glow on Lucy's face that confirms her mother's predicament. "I got such a buzz, I can't wait to do it again," she insists.
It is now the turn of graphic designer Manda Friend whose only preparation has been "dodging London tourist buses" on her Suzuki 550. Rolling yet another cigarette she looks down at the ringmaster who could so easily become her executioner. Though she is convinced she has "a 60 per cent chance of falling off", she is still looking forward to the experience. "The worst bit is trying to walk off the bike and sit down. You're so dizzy you can't walk straight," Sarah Kells, the first volunteer, warns her as she descends the stairs to the pit.
Not to be confused with the pedestrian fairground version, The Motordrome Company's Wall of Death, built in 1932, has toured the country's motorcycle events for the last eight years, reviving an archaic yet heart-stopping act.
Once a regular feature of the fairgrounds in the 1930s, rival Wall of Death riders would roam the country offering spectators stunts more outrageous than the other. But changes in public taste have forced most of them off the road.
At this year's Chelsea Bridge show, Cham is by now on her fourth brush with the wall. What was initially "a once in a lifetime opportunity" has become an hourly chore as The Wall of Death's neon sign draws the evening crowds. "I'm not scared any more", she says, "it's really no more dangerous than riding a bike in London."
The Motordrome Wall of Death: Kent Custom, Romney Marsh, Kent, 7-9 Jul; 1000 Bikes, Snetterton, Norfolk, 15-16 Jul. C4 will be screening a documentary, 'Girl on a Motorbike' for Short Stories on 6 Jul