How about 25 laps of the Corus Tube Works. Winner will be the last person to drop dead from any of the following:
1) Inhaling 5kgs of iron filings
2) Being run over by a 44t lorry (an unfortunate accident)
3) Being run over by site security (possibly on purpose)
4) Falling in one of their impressive potholes
5) Being beaten up by a swaggering plastic jock