An officer who missed a gun while arresting the killer of his colleague admitted he abandoned training and should have discovered the weapon.

Metropolitan Police sergeant Matt Ratana was murdered on September 25 2020 by Louis de Zoysa, 26, who opened fire with an antique revolver at a Croydon custody suite.

De Zoysa, who is autistic, had earlier been arrested and searched but officers failed to find the gun he had in an underarm holster despite discovering bullets in his pocket.

Pc Richard Davey, the officer who carried out the search along with Pc Samantha Still, told an inquest at Croydon town hall on Wednesday: “The weapon was there, I should have found it, if not the weapon, the holster.”

Dominic Adamson KC, representing Sgt Ratana’s partner Su Bushby, identified four occasions where Pc Davey “failed to do the job you were supposed to do”.

The lawyer asked: “If you had done your job properly Sergeant Ratana would still be alive, wouldn’t he?”

The officer answered: “I don’t know.”

Senior coroner Sarah Ormond-Walshe asked Pc Davey if there had been any missed opportunities.

The officer replied: “The opportunities missed were a result of my decision to consider the safety of Mr De Zoysa, myself and Pc Still.”

Pc Davey agreed with Mr Adamson that an adequate search would have identified the gun.

He said: “I believed at the time it (the search) was adequate but with hindsight no.”

The officer agreed he did not follow police training by ignoring the Met’s policy of searching “top-down”.

He said: “Having seen the body-worn footage, I should have adopted Metropolitan Police policy.”

Pc Davey later added: “If I was to go back I would have done everything by the book.”

Mr Adamson accused Pc Davey of not thoroughly searching De Zoysa’s back, saying he merely “floated” his hand over it, which the officer denied.

Having been shown footage of the arrest in London Road, Norbury, at around 1.30am that day, Pc Davey was asked by Richard Furniss, counsel to the inquest, why De Zoysa’s upper back had not been checked thoroughly.

The officer replied: “I believe I gave him a thorough search where a firearm could have been secreted.”

He told the inquest De Zoysa was detained because he was wearing a hat and overcoat in warm weather amid concerns over burglaries in the area.

De Zoysa initially admitted possessing cannabis which made Pc Davey feel the gunman “had something that he shouldn’t”.

He was told numerous times by the officer to stop reaching into his coat pocket, where the bullets were discovered.

Mr Furniss put to Pc Davey that he had used the “incorrect technique” during his search, to which the officer said: “I felt it necessary to deviate from the policy to check his pockets.”

Your Local Guardian: A weapon (circled in red) laying on the floor, as officers wrestle Louis De Zoysa to the floor, moments after Sergeant Matt Ratana was fatally shotA weapon (circled in red) laying on the floor, as officers wrestle Louis De Zoysa to the floor, moments after Sergeant Matt Ratana was fatally shot (Image: PA)

Pc Davey, who was a probationer at the time, also said he could not recall if he had seen the Met’s stop and search policy or documents on how to deal with people with autism.

The officer, asked by Mr Adamson why he did not question if de Zoysa had a gun, said: “I thought if he came forward about the drugs he would have come forward about being in possession of a firearm.”

He denied the suggestion it would have been an “obvious” question to ask.

In the custody van, De Zoysa was seen in footage wriggling and jerking, which according to expert evidence was him repositioning the firearm to his hands.

However, Pc Davey said he was “interrupted” while filling out paperwork and did not spot this.

The officer admitted that had he been constantly monitoring De Zoysa and seen this, he would have “considered” a second search.

Mr Adamson said: “You haven’t done a search in accordance with your training, you haven’t performed the role of an escorting officer in accordance with training.”

After arriving at Croydon’s Windmill Road custody centre, De Zoysa was allowed to walk without an officer gripping his arm, or handcuffs.

Pc Davey said this was because De Zoysa looked “nervous” and he did not want to “panic him further”, later saying this was the wrong decision.

The officer also said he could not see De Zoysa’s hands hidden under his jacket and admitted he should have exposed them.

De Zoysa later managed to move his handcuffed arms from behind his back to fire at Sgt Ratana.

The New Zealand-born officer, 54, who had served in the Met Police for almost 30 years and was three months from retirement, was hit in the chest by the first of three shots discharged by De Zoysa within three seconds.

A second bullet struck him in the thigh before De Zoysa was wrestled to the ground by other officers, as a third round hit the cell wall.

Former tax office data analyst De Zoysa, who was living in a flat on a farm in Banstead, Surrey, discharged a fourth shot while on the cell floor, hitting an artery in his own neck and causing him brain damage.

He is serving a whole-life jail term for Sgt Ratana’s murder after a trial earlier this year, during which his legal team argued that he was suffering an autistic meltdown at the time of the shooting.

The three-week inquest continues.