RobT and Grunos
My thought on the prize was that there is no reason why both should not be true ie a prize for the first correct entry plus the usual £100 prize drawn at random from all correct entries by the end of the month. Indeed that approach would make sense to me, because presumably the Guardian doesn't want to discourage entries from those who might think that after X days, their chances of winning a prize have gone. Fingers crossed anyway.
And just to record my thanks to Enigmatist for a very enjoyable puzzle. All in all I have really enjoyed the way the Guardian has marked the 30,000th puzzle. I'm not counting on seeing the 40,000th (mid-April 2058?), but there'll be a centenary in 2029 and perhaps the Guardian can be encouraged to mark puzzle 33,333 (a little after Christmas 2036?).