A gun and a railway sleeper were found in a van raided by police in an armed robbery operation this morning in Wanstead High Street, the Guardian understands.

Heavily armed police surrounded and swooped on the white vehicle close to Wanstead Pharmacy at around 9am.

A man, thought to be aged in his 30s, was arrested at the scene.

The Guardian understands that police are investigating the possibility that the railway sleeper was intended to be used as part of a smash-and-grab raid on a bank.

A witness has also posted a photograph on the website Twitter showing flying squad officers at the scene pulling what appears to be a handgun out of a bag next to the van at the scene.

There is also note outside the HSBC bank in the High Street saying it is closed due to an incident, raising speculation that it could have been the target for the alleged attempted robbery, although this has not been confirmed.

Witnesses said passers-by ran for cover when police swooped on the van and reported hearing loud bangs.

The Met initially denied any shots were fired but later confirmed 'Hatton' rounds were shot at the van's tyres to disable it.

The Guardian is awaiting further details from police.

Part of Wanstead High Street remains closed.