A unanimous jury took less than 90 minutes to clear Simon Walsh, 50, whose Hotmail user name was ‘Cityfister’ and who surfed a social networking website called ‘nasty kinky pigs’.

Walsh told police he was interested in BDSM and had practised fisting, but he disputed the images were extreme pornography.

He told the court he had ever hurt anyone, saying: "I know the limits and I respect them."

He was charged with possessing email attachment images found by police on a Hotmail server account set up to receive and send sexual messages.

Three of the images were of urethral sounding, a practice where a medical instrument is inserted into the penis, stretching the urethra and stimulating the prostate.

Walsh admitted to taking the pictures at a party and said he had only sent them only to other participants at the party.

The defence had argued there was no evidence of any serious injury in any of those images, or ones of anal fisting, and that the activities were low risk

Walsh’s case is understood to be the first to address whether images of anal fisting, which is legal, and urethral sounding are "extreme" pornography, as defined under the controversial section 63 of the Criminal Justice and Immigration Act 2008.