London underground (illustration)
London underground (illustration)Reuters

A terror attack in the UK is a matter of "when, not if", the commissioner of the Metropolitan Police warned Sunday, according to the Independent.

Sir Bernard Hogan-Howe said he cannot promise an attack will not take place, despite being the man in charge of preventing them.

He said instead he could offer reassurance by explaining what police and security services are doing to protect the public.

"I feel and understand that fear, and as the police officer in charge of preventing such an attack I know you want me to reassure you,” he said of the terrorist atrocities Europe has seen recently.

"I am afraid I cannot do that entirely. Our threat level has been at 'Severe' for two years. It remains there. It means an attack is highly likely – you could say it is a case of when, not if," added Hogan-Howe.

Explaining the work of the police, he pointed to the number of terror plots that had been foiled since the murder of soldier Lee Rigby in May 2013, including one to murder officers at Shepherd's Bush police station, west London, and another to carry out a Lee Rigby-style attack on U.S. soldiers in East Anglia.

He further said the relationship between the police, MI5 and MI6 was a "world-beater" which has given the UK an intelligence advantage and said the nation's gun control laws helped make it difficult for terrorists.

“Now our resilience has increased as all Met officers who carry a gun have been trained to go forward and take the initiative, in the face of a new terrorist threat,” said Hogan-Howe, according to the Independent.

“Meanwhile we are training hundreds of extra officers so they are ready to supplement our numbers during an attack similar to that seen in Paris. This increases overall numbers of firearms officers by 600 to 2,800,” he added.

Terrorism has been a concern for Europe, as can be evidenced by the recent attacks in Nice, Normandy and Wurzburg, Germany.

London has also been affected by terrorism in recent months. In December, a Muslim attacked the London Underground, slashing the throat of a passenger for “his Syrian brothers”.