What's the briefest you can wear in British pools?

[Torchwatch]

I usually wear 2" side speedos in UK swimming pools without any issues. I have worn slightly brief than that but not recently.
Most of the Lifeguards are swimming club members and are familiar with swimmers in speedos for training and racing and should have no trouble for you.
The problems come from small girls of a certain age who may begin tittering and pointing. You would no doubt ignore them but other people may notice them add 2 and 2 to get 5.
As I write this the early morning sun is shining and the birds are singing, try wearing your 1.5" bikini on the beach to discover how people react to it before taking it to a pool.
I believe in pushing the envelope and leading by example but suggest you wait until a few more guys are wearing brief swimwear before going for very brief swimwear yourself in a public pool. Being a trend setter doesn't work if no one is following your trend.