I can see how with someone who had had some booze, a very small diameter needle might not even be noticed, but it sounds utterly psychopathic, as well as being utterly undeniable if caught in the place and liable to lead to a massive immediate sentence (though spiking of any kind should be treated as GBH with intent imo).
edit: I looked at the Nottingham article - that club in Nottingham, under it's old name, was the most depressing club I ever went into exactly due to an apparent culture of spiking. I'd never even noticed women covering their drinks before so that nothing could be slipped into it, but here it was all of them. I was often guarding the drinks for the women in the group I was with when they went to the loo. Tbh, if this was to happen anywhere, it would be there.