Ex-St James’s Hospital porter Thomas Shelton, 63, was convicted by a Leeds Crown Court jury of a string of sex offences against girls, some as young as 10.

And the court heard how more than 40 years ago Shelton was jailed for his part in an Army “committee of execution” in Malaysia.

The jury found Shelton, formerly of Shakespeare Court, Burmantofts, was guilty of 10 rape charges, three counts of indecent assault, one of gross indecency and four counts of child cruelty.

The charges dated from the 1960s to the early 1980s

Jailing him for 20 years, Judge Peter Hunt told Shelton: “These convictions disclose a degree of wickedness that really is almost impossible to contemplate.

“It has taken a very long time, but eventually as it always will, the law has caught up with you….The complainants have been struggling against all the odds to come to terms with the emotional and psychological damage you have done to them”

In a statement read to the court one victim stated: “I feel he is a nasty and evil man…He caused people to be so terrified of him.”

He was made the subject of a Sexual Offences Prevention Order banning him from ever working with or having unsupervised access to children.

Shelton, who worked as a porter at St James’s Hospital from 1987 to 2005, showed no emotion and said “thank you” to Judge Hunt as he was led to the cells to start his sentence.

The court heard how Shelton was jailed for three years and drummed out of the Army in 1965 after a court martial convicted him of attempted murder in Sarawak.

Shelton, then aged 20, was one of four British soldiers from the Argyll and Sutherland Highlanders who formed a “committee of execution” to kill a village leader because they suspected him of aiding the Indonesians in the Indonesian-Malyasian confrontation of 1962-66.

The gang drew lots to decide who should throw a grenade into the man’s bungalow.

The grenade was thrown but it did not explode and their intended victim hurled it back through the window