The British government saw "Abdullah al Andalusi" as a trusted adviser, someone qualified to help oversee Her Majesty's Inspectorate of Constabulary (HMIC), which supervises UK police counter-terrorism policy and reactions to attacks.

Andalusi may have enjoyed access to classified information in that role. That stopped when someone in the HMIC hierarchy recently saw Andalusi on television, defending extremist ideology offered by the Saudi-financed Muslim Debate Initiative, the Sunday Telegraph's Andrew Gilligan reported.

Andalusi's Islamist activities were done under his real name, Mouloud Farid, while government officials failed to realize he secured government work with a fake name. Farid is close with the radical Hizb ut Tahrir, a global Islamist movement that has been described as a "conveyor belt" for jihadist terror.

Andalusi, speaking under his real name Farid, preached that ISIS terrorists were "no different to Western armies," and said the British government wanted to destroy Islam.

"He despised Britain, yet worked for the British government," an unidentified associate told Gilligan. "He would talk about the right of oppressed people to take up arms against the oppressor and yet he was overseeing the police."

Within the inspectorate, Andalusi was promoted to a management position described as "at the heart of the security establishment." People in similar positions have "access to highly sensitive and classified police and intelligence information to carry out their inspections," Gilligan reported.

Andalusi has said Muslims "would be jubilant at the return of the caliphate [Islamic state], which is a vital obligation upon Muslims that has been conspicuously missing for so long."

Members of Parliament are demanding an investigation into how Andalusi's dual lives were missed by government officials. "This man's unsuitability for sensitive work should have been obvious from the start," said Labour MP Khalid Mahmood.

Read the full Telegraph story here.