Originally Posted by Rosie

BDSM and the law is a really grey area here in the UK - but red welts are not illegal per se.

The general rule of thumb here is that if a welt disappears within three days and doesn't require medical intervention then it's acceptable in law - if it takes longer than three days to heal then the dominant can be charged with grevious bodily harm and the submissive can be charged with aiding and abetting an assault on their own body.

In practise the only reason they put the spanner men away was because they were gay. As far as I know, no hetero BDSM couple have been charged with anything similar.