An astrophysicist has been jailed for 15 months after admitting owning 500,000 indecent images of children.
Robin Phillips was a leading scientist at a Canadian university
Robin Phillips was caught taking photos up the skirt of a girl playing on one of the lions in Trafalgar Square.
The 33-year-old's child porn collection was thought to be the largest yet seen in the UK, Southwark Crown Court heard.
Phillips, of East Grinstead, West Sussex, was banned from having a camera in public for 10 years and was told to register as a sex offender.
He was also disqualified from working with children for life.
'Largest porn collection'
Judge Paul Dodgson told him the scale of his offending meant a prison sentence was inevitable.
He added: "I accept you had no physical contact with any young girls but the taking of pictures such as these exposes them to long-term sexual abuse.
"It is not natural for 11 to 12-year-olds to pose in this way."
The Canadian-based scientist has since lost his job at the University of Lethbridge in Alberta.
The court heard that Phillips had built up his porn collection during "a decade of dedicated downloading".
Phillips was caught taking pictures of young girls in Trafalgar Square
In Trafalgar Square, he was seen "in an agitated and frantic state, hurrying backwards and forwards in front of the lions near Nelson's Column", the court heard.
After he was arrested, he admitted "photographing females" but described it as "just a bit of fun, more of a hobby" - he said he never suspected it was illegal.
Detectives discovered the extent of his activity when they examined his laptop at his parents' home in Cansiron Lane, Sussex.
Prosecution lawyers claimed it was "perhaps the first step towards more serious offending".
The judge said Phillips did not pose a "significant risk of serious harm in the future".
His defence lawyer said he now saw the seriousness of his behaviour and had funded counselling for himself.