A former teacher has admitted to abusing children in the UK and abroad for more than 25 years in what is described as one of the worst cases ever seen in a British court. Mark Frost - formerly known as Andrew Tracey - aged 70, admitted a total of 45 offences including rape, sexual assault, inciting sexual activity with a child and making indecent images against his victims, all ages between 10 and 15.

The court heard how Frost abused children while working as a teacher in Worcestershire as well as in Thailand. He had already admitted 22 offences while in the Asian country in July 2016, and pleaded guilty to 23 offences against boys in the UK and Thailand when appearing at the Old Bailey today (1 February).

The National Crime Agency (NCA) fears that Frost, who worked as a teacher in England from the 1970s until the 1990s and was also involved with the Scouts until 1991, may have more victims and are urging others to come forward. At least one of Frost's victims died before he was brought to justice.

Frost was arrested in 2013 by the Royal Thai Police after one victim came forward with allegations. He was arrested but fled the country while on bail. He briefly returned to the UK in 2014, but could not be arrested as there was no warrant for his arrest and he was not wanted for any outstanding offences in the UK.

He was eventually arrested in Spain in March 2016 after the NCA and Dutch National Police gathered enough evidence to obtain a European Arrest Warrant. Dutch police believed Frost was in contact with one of their citizens while abusing children in Thailand.

Following a search of his address in Spain, a laptop and other digital devices were recovered and found to contain more than 1,000 indecent images of children.

Frost was extradited to the UK in April 2016 using Section 72 legislation, which allows UK nationals to be prosecuted in the UK for offences committed overseas. He was charged with 22 offences including contact sexual abuse of boys aged between 10 and 14 in Thailand.

Frost plead guilty to 17 offences on 1 July and admitted the remaining five on 1 September 2016. Appearing at the Old Bailey, the serial paedophile has now plead guilty to a further 23 offences against children.

Ruona Iguyovwe, Senior Specialist Prosecutor in the CPS International Justice and Organised Crime Division, said: "The harrowing evidence presented by the prosecution in this case outlined the suffering that Mark Frost caused to his victims. Over many years, Frost repeatedly exploited vulnerable young victims, both in the UK and in Thailand, for his own sexual gratification.

"He systematically targeted and groomed children from a poor community having sought to attract and lure them to his house through apparent generosity. He also photographed and filmed his own abuse of the children and shared it online. His offending has caused severe psychological harm to all of the children he abused, many of whom are now old enough to realise the enormity of what happened to them.

"The CPS worked with investigators from a very early stage in order to build a strong case to secure these convictions, including travelling to Thailand to offer on-the-spot advice as victims were interviewed for the first time.

"International borders are not a barrier to justice and this prosecution was made possible through detailed partnership working between the CPS, the National Crime Agency and prosecutors in both Europe and Thailand."

Andy Brennan, Deputy Director of the NCA's CEOP Command said: "This has been a lengthy and complex investigation into a prolific child sex offender, who over many years believed he could sexually abuse children and evade law enforcement.

"The weight of evidence gathered by the investigating officers in this case was such that Frost plead guilty to over 40 charges. Safeguarding work is on-going with victims we know about already, both in the UK and in Thailand and we will continue to ensure victims receive the appropriate support as required.

"However, we suspect there could be many more victims of Frost, both male and female, who have never come forward or spoken to anybody about what happened to them."