Police said no blame should be attached to the hospital
A convicted paedophile has been arrested while working as a children's nurse in a north-west London hospital.
Lars Gellner, 37, was arrested at work at Northwick Park Hospital in Harrow.
He had been convicted in his absence in Cambodia for attacks on boys but was able to get through security checks as he has no European criminal record.
A Home Office spokesman refused to comment on the case but it is believed Gellner is being held at a remand centre while his future is decided.
Gellner, who is German, had been arrested in October 2008 after applying for a UK visa for a 14-year-old Burmese boy he wanted to bring here.
Sex offenders register
A British embassy official recognised his name from reports about him fleeing Cambodia.
He had been placed on the sex offenders register by a magistrate after his arrest and charged with fraud for his failure to include his criminal record on his job application.
But the case against him was thrown out on Thursday by a judge at Aylesbury Crown Court because of a problem with documents sent from Cambodia.
But the government can deport him to Germany because he had been sentenced to more than 12 months in prison for his original offence.
Det Sgt Sam Hayward said: "Our team have stopped this man creating more child victims in this country.
"But no blame should be attached to the hospitals. They did everything they could to carry out the criminal checks on him and they came back showing nothing."
A spokeswoman for North West London Hospitals Trust said Gellner had worked a small number of shifts at Northwick Park Hospital last October.
She added: "He was employed through an agency and we can confirm that they conducted an enhanced Criminal Records Bureau check.
"Our contracts with employment agencies stipulate that CRB checks must be carried out on staff supplied to us."
Christine Beddoe, director of End Child Prostitution and Trafficking, said: "This highlights the gaps and weaknesses of international sex offender management which puts children at risk here.
"If the home secretary is serious about getting tough on sex offenders who travel abroad, she should be making all efforts to close loopholes and work more closely with counterparts in Europe and Asia."