A SECRET vault of child porn led to the arrest of a paedophile rights campaigner, a court has heard.

Thomas O'Carroll, 61, who was arrested at his home in Shildon, County Durham, in January, led a worldwide campaign to legalise child sex.

Yesterday, a crown court in London heard how O'Carroll, 61, and accomplice Michael Studdert, 67, a millionaire former priest, spent years building up an "Aladdin's cave" of child porn.

Police discovered an elaborate vault in Studdert's bathroom at his sprawling country estate in Surrey, which contained one of the largest collections they had ever found -of more than 50,000 indecent images.

O'Carroll, a former teacher and journalist, founded the now-defunct Paedophile Information Exchange and has a criminal career stretching back 15 years.

The police inquiry was launched in May 2002 and an undercover officer, known by the pseudonym Derek Longton, befriended paedophiles and was introduced to O'Carroll.

Peter Zinner, prosecuting, said: "So began a lengthy relationship between the two men, during which O'Carroll openly discussed his sexual interest in children and said he had in his possession or had access to paedophile pornographic material."

In the spring of last year, O'Carroll gave the officer a box of videos and slides containing hundreds of images.

A fingerprint on one of the items was matched to Studdert and police raided his home.

The search lasted four days until a compartment containing child porn was discovered behind a false wall in a bathroom.

Mr Zinner said: "A particularly alert police officer then noticed a hook with a small rag hanging on it.

"When he pulled the hook, a lengthy piece of dowel came out of the wall.

''That released an adjacent panel which, in turn, revealed a doorway and a further secret vault behind the bathroom wall.

"That secret vault was an Aladdin's cave of every conceivable format of child porn. There were videos, photos -both amateur and professional -cine films, magazines and slides."

The stash included pictures of children, some as young as six, being raped and tortured.

Studdert admitted 20 charges of making indecent images of children, one of distributing them and one of possession.

O'Carroll, now of Leamington Spa, Warwickshire, admitted two charges of distributing child porn images.

The case was adjourned until Wednesday for sentencing.