More than 900 vehicles have been stopped and checked before using the A12 Blackwall Tunnel in the past three months, latest figures reveal.

Police are now carrying out a permanent crackdown on unsafe vehicles to prevent accidents that result in tunnel closures.

The stop-checks have resulted in four arrests and more than 400 fines for offences including bad-maintenance and drivers not complying with height restrictions.

The Met police set up a permanent team in September to keep one of London’s most congested bottlenecks flowing, in a joint scheme with TfL following an earlier 12-week pilot.

The team has cut by more than half the time it takes to respond to breakdowns and accidents. It has reduced the average delay reopening the tunnel each time from 35 minutes down to 16.

New monitoring equipment on the approach to the northbound carriageway is also being used to detect lorries too big to get through the oldest of the twin tunnels, first opened in 1898, before they arrive. Some 800 lorries have been diverted away from the tunnel since November.