American teacher and prolific paedophile William Vahey drugged and preyed on up to 90 young teenage boys around the world

The scale of abuse carried out by a convicted paedophile on pupils at a private London school was described by its chair of governors as “the worst thing” he has ever been involved in during 40 years of education.

Sir Chris Woodhead, the former Ofsted Chief Inspector, confirmed ex-teacher William Vahey had preyed on children at the independent Southbank International School and said it made him feel physically sick when he heard what had happened.

American citizen Vahey, 64, killed himself last month, two days after investigators filed a warrant to search a computer drive containing pornographic images of at least 90 boys aged from 12 to 14 who appeared to be drugged and unconscious meaning many of the victims may still be unaware they were abused. It is believed that all of the boys in the images were his students going back to 2008 – Vahey taught history and geography to pupils at the London school from 2009 until last year.

It is not clear exactly how many children in England have been affected, although the FBI, which is working with the school to identify affected children, said it was searching for up to 90 potential victims from international schools around the world. Vahey also taught in Indonesia, Saudi Arabia, Madrid, Athens, Venezuela, Iran and Lebanon, managing to slip through the net for decades despite being jailed for child sex offences in California in 1969.

Sir Chris said that parents at the London school, which teaches children aged three to 18, were very concerned and that it “beggars belief” Vahey was able to teach for so long while harbouring the conviction.

Photo issued by the FBI of American William Vahey Photo issued by the FBI of American William Vahey (PA)
He said: “Everyone at the school is deeply shocked by what we heard. Our two priorities now are to communicate as much information as we have as quickly as we can, and to help the police as much as we can in what is now an international police inquiry into the activities of this man.”

Sir Chris said Vahey, who mainly taught pupils aged between 11 and 14 but also took students out on trips, had an “immaculate record” and had never given any staff at the school any cause for concern. He said: “He was a very popular man, both with staff and students. He has managed to deceive his colleagues in schools all around the world for 30 years… This is the worst thing that I’ve ever been involved in in 40 years of education.”

A meeting at the school which police and other investigators will attend is due to be held next week. Special Agent Patrick Fransen from the FBI said: “I’ve never seen another case where an individual may have molested this many children over such a long period of time. I'm concerned that he may have preyed on many other students prior to 2008.”

Vahey’s abuse caught up with him when he was confronted about the images by a colleague at the American Nicaraguan School in Managua, Nicaragua, where he had most recently been teaching. He confessed that he was molested as a child and had preyed on boys all his life, plying them with sleeping pills before abusing them. The photos were catalogued with dates and locations that corresponded with overnight field trips that Vahey had taken with students since 2008, but he had led pupils on such outings for his entire career.

Vahey, who had a home in London as well as in South Carolina, was found dead in Luverne, Minnesota, on March 21.

Scotland Yard said it was helping the FBI with its inquiries. A spokesman said: “Officers from the sexual offences, exploitation and child abuse investigation team are assessing and evaluating intelligence passed to the Met by US authorities, and actively seeking any evidence whilst working with partner agencies to ensure that potential victims are supported.”

Start your day with The Independent, sign up for daily news emails
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

Day In a Page

General Election 2015: Chuka Umunna on the benefits of immigration, humility – and his leader Ed Miliband

Chuka Umunna: A virus of racism runs through Ukip

The shadow business secretary on the benefits of immigration, humility – and his leader Ed Miliband
Yemen crisis: This exotic war will soon become Europe's problem

Yemen's exotic war will soon affect Europe

Terrorism and boatloads of desperate migrants will be the outcome of the Saudi air campaign, says Patrick Cockburn
Marginal Streets project aims to document voters in the run-up to the General Election

Marginal Streets project documents voters

Independent photographers Joseph Fox and Orlando Gili are uploading two portraits of constituents to their website for each day of the campaign
Game of Thrones: Visit the real-life kingdom of Westeros to see where violent history ends and telly tourism begins

The real-life kingdom of Westeros

Is there something a little uncomfortable about Game of Thrones shooting in Northern Ireland?
How to survive a social-media mauling, by the tough women of Twitter

How to survive a Twitter mauling

Mary Beard, Caroline Criado-Perez, Louise Mensch, Bunny La Roche and Courtney Barrasford reveal how to trounce the trolls
Gallipoli centenary: At dawn, the young remember the young who perished in one of the First World War's bloodiest battles

At dawn, the young remember the young

A century ago, soldiers of the Empire – many no more than boys – spilt on to Gallipoli’s beaches. On this 100th Anzac Day, there are personal, poetic tributes to their sacrifice
Dissent is slowly building against the billions spent on presidential campaigns – even among politicians themselves

Follow the money as never before

Dissent is slowly building against the billions spent on presidential campaigns – even among politicians themselves, reports Rupert Cornwell
Samuel West interview: The actor and director on austerity, unionisation, and not mentioning his famous parents

Samuel West interview

The actor and director on austerity, unionisation, and not mentioning his famous parents
General Election 2015: Imagine if the leading political parties were fashion labels

Imagine if the leading political parties were fashion labels

Fashion editor, Alexander Fury, on what the leaders' appearances tell us about them
Phumzile Mlambo-Ngcuka: Home can be the unsafest place for women

Phumzile Mlambo-Ngcuka: Home can be the unsafest place for women

The architect of the HeForShe movement and head of UN Women on the world's failure to combat domestic violence
Public relations as 'art'? Surely not

Confessions of a former PR man

The 'art' of public relations is being celebrated by the V&A museum, triggering some happy memories for DJ Taylor
Bill Granger recipes: Our chef succumbs to his sugar cravings with super-luxurious sweet treats

Bill Granger's luxurious sweet treats

Our chef loves to stop for 30 minutes to catch up on the day's gossip, while nibbling on something sweet
London Marathon 2015: Paula Radcliffe and the mother of all goodbyes

The mother of all goodbyes

Paula Radcliffe's farewell to the London Marathon will be a family affair
Everton vs Manchester United: Steven Naismith demands 'better' if Toffees are to upset the odds against United

Steven Naismith: 'We know we must do better'

The Everton forward explains the reasons behind club's decline this season
Arsenal vs Chelsea: Praise to Arsene Wenger for having the courage of his convictions

Michael Calvin's Last Word

Praise to Wenger for having the courage of his convictions