www.spectator.co.uk/article/are-sex-offenders-exploiting-trans-rights-policies-behind-bars-
According to this recent article, by James Kirkup in the Spectator on 19th January, the most recent statistics available from the Ministry of Justice show that 18% of the men in prison who aren't trans identified, are currently serving time for sexual offences.
Amongst those who identify as transwomen, the percentage jumps to "between 60 and 61.3%". (That's those who don't have a GR certificate, because statistics covering those with a GRC are harder to separate out from the female prison population and are not yet available).
I believe women have been banned from twitter for sharing these official government statistics. Some people feel very strongly that this is information that needs to be kept out of the public sphere.