A Walmer cyber geek has admitted attempting to blackmail Halifax bank by threatening to release the details of 28,000 account holders to The Sun newspaper.

Lewys Martin demanded one bitcoin – an untraceable virtual currency – for every 10 sets of details he was holding on a memory card.

The 22-year-old was also caught with three malware phishing programmes designed to steal personal information and data.

Appearing at Southwark Crown Court in a purple polo shirt and black glasses via prison video link, Lewis admitted blackmail and two counts of possession of articles for use in fraud.

He also pleaded guilty to possessing an indecent photograph of a child at level five on the Copine scale, which depict deliberately posed erotic scenes.

Lewis entered a further guilty plea to possessing a further eight photographs of children at level four, which show poses suggesting sexual interest.

Martin, formerly of Dover Road, was jailed for two years in May 2013 for using his IT expertise to launch cyber attacks on the websites of Oxford and Cambridge universities.

He inundated the websites with requests for so much information their servers fell offline.

Fortunately the universities had "solid protection programmes" in place and no sensitive information was disclosed.

Kent Police also suffered an attack at the hands of Martin in February last year, leading to its public website going offline for more than an hour.

Sentencing was adjourned for reports to be prepared, which may include reports on autism and Asperger's syndrome.

Judge Peter Testar said: "The defence must of course appreciate that these are very serious offences and can lead to serious consequences.

"The fact that I am asking for reports from probation services should not mislead you about that.

"It is really just so that the court has the most information about you that it can possibly have. These are serious matters."

Martin, who is being held in custody at Wandsworth prison, will return to court for sentencing on October 16.