Isis Daesh Lebanon
Detailed information about 22,000 members of Islamic State has been hailed as a major breakthrough in the fight against terrorREUTERS/Ali Hashisho

Counter-terrorism experts have hailed the leak of documents containing detailed information about 22,000 Isis militants – including dozens from the UK – as the biggest breakthrough ever in the fight against Daesh.

The information, including the names, addresses and telephone numbers, was completed by new recruits to Isis and was on a memory stick stolen from the head of Islamic State's internal security police. The information was obtained by Sky News, who were contacted by a former Isis member called Abu Hamed who had become disillusioned with the organisation.

Anyone wishing to join Isis had to complete all 23 questions on a form. The questions include details of their education, families and phone numbers - many of which are thought to belong to the militant themselves. The forms also provide information on who recruited the jihadist to Isis. Jihadis from at least 51 countries from across North Africa, Europe, the US and further afield are on the list.

The documents are being analysed by counter-terrorism experts. Former global terrorism operations director at MI6 Richard Barrett said: "It's a fantastic coup. And it will be an absolute goldmine of information of enormous significance and interest to very many people, particularly the security and intelligence services."

Among those whose full details are included on the list are well-known Jihadis like Reyaad Khan from Cardiff, Junaid Hussain from Birmingham - the husband of former punk singer Sally Jones, also listed - and Abdel Bary, the London rap singer. Khan and Hussain have both been killed, the whereabouts of Jones and Bary are still unknown.

Crucially the documents also give information about dozens of British jihadis who were previously unknown to security services. Some may already have returned to the UK and are now being traced to see if they are a danger to the country.

In the UK, individuals who return from Iraq and Syria and from taking part in the conflict in Daesh areas are subject to an investigation to determine whether any crimes have been committed abroad or whether the individual represents a threat to national security. The Home Office looks at the individuals on a case by case and investigations and prosecutions take into account a wide range of evidence.

Pro-opposition Syrian news website Zaman al Wasl, which has published a selection of the forms online, claims only 1.7% of those listed are Syrians. Of the foreign fighters, the largest number are Turks and France has the highest number of recruits from Europe. One Isis brigade is composed exclusively of those wishing to die in martyrdom operations.

As for Abu Hamed, who leaked the documents, he says he left the group because it had been taken over by Iraqi Baathists loyal to former dictator Saddam Hussain and was now retreating from Raqqa and the rest of Syria back to its spiritual home of Iraq. Hamed also claims Isis are in league with the Syrian government and Kurdish YPG to fight the moderate rebels, though as yet there is no independent confirmation of the claim.