Actually, for the 1/1,000,000 chance of GBP 10,000,000,000 then GBP 1,000 seems OK? My EV is GBP 10,000 or 10.0 times my stake, which is _much_ better that buyi

Actually, for the 1/1,000,000 chance of GBP 10,000,000,000 then GBP 1,000 seems OK? My EV is GBP 10,000 or 10.0 times my stake, which is _much_ better that buying 1,000 lottery tickets at GBP 1.00 each, for a 1/14,000 chance of GBP 10,000,000 (nominal; neglecting rollovers) and an EV of GBP 714.28 (approximately) which is an under unity gain (0.71 of the stake returned). However using the Kelly criterion for placing bets, I think it turns out that even though the return is high for the ten billion wager, you should only place the GBP 1,000 bet if you have a bankroll of 1,000,000,000 already ;( Corrections to my maths welcome!