The senior police officer leading the investigation into Streatham terrorist Sudesh Amman has denied suggestions from his family’s lawyer that the undercover operation was a failure.

The officer, known only as HA6 to protect his identity, stated there was a lack of evidence against 20-year-old Amman in the days before he struck on February 2 2020, stabbing and injuring two members of the public in broad daylight before being shot dead by armed police.

He said police actions that day prevented further tragedy.

Giving evidence at the inquest into Amman’s death on Friday, at the Royal Courts of Justice, the senior officer said: “This is a view held by my peers.

“The professionalism and the bravery of those officers and what they prevented … it could have been far, far worse.

“For those of us in the investigations team, we are grateful for their actions on that day.”

The inquest previously heard how Amman was deemed to be “one of the most dangerous individuals” that police and MI5 teams had investigated, and that police feared an attack would be “when, not if” during discussions a fortnight ahead of his release.

He was automatically released from Belmarsh prison on January 23 2020, part-way through a 40-month sentence for obtaining and disseminating terrorist materials.

This was despite police pleas to the Belmarsh governor to detain Amman for longer after intelligence suggested he maintained an extremist mindset, wanted to carry out a knife attack in the future, and pledged allegiance to the leader of so-called Islamic State.

Amman, who is originally from Coventry and of Sri Lankan descent, but was previously of Harrow in north-west London, spent 10 days living in a bail hostel in Streatham, south London, during which time undercover police teams monitoring him remarked at his “concerning” behaviour.

Amman was seen by covert police buying four bottles of Irn-Bru, kitchen foil and parcel tape from a local Poundland on January 31, items which were used to fashion a fake suicide belt he wore during his rampage on Streatham High Road two days later.

But they said there was not enough evidence to arrest him and feared searching his room would blow their cover.

Rajiv Menon QC, for Amman’s family, accused police of making “the wrong call” not to intervene at the time.

HA6 replied: “Given the threat he posed, the methodology of the attack, I would counter that by saying the police stopped an attack that could have been far, far worse.”

He added: “If he (Amman) had been arrested, he would have been back out in the community and would have had an operational advantage.

“It would have made our response harder.”

The inquest continues.