Is it legal? ...

Protection of Children Act 1978 (England and Wales)
The law on images of child abuse is clear. It is an offence to take, permit to be taken, make, possess, show, distribute or advertise indecent images of children in the United Kingdom. The word indecent should be taken at its dictionary meaning; as a guide it means any images of children, apparently under 18 years of age, involved in sexual activity or posed to be sexually provocative.

Obscene Publications Act 1959 & 1964
The law makes it an offence to publish, whether for gain or not, any content whose effect will tend to "deprave and corrupt" those likely to read, see or hear the matter contained or embodied in it. This could include images of extreme sexual activity such as bestiality, necrophilia, rape or torture.

Public Order Act 1986
The law covering criminally racist material makes it an offence to stir up racial hatred against a group of persons in Great Britain defined by reference to colour, race, nationality (including citizenship) or ethnic or national origins.