Urgent repairs are set to start tonight on a busy tunnel following a bridge strike earlier this week.

Motorists travelling through the Roundhill Tunnel in Folkestone have been warned to expect delays.

Yesterday, National Highways closed one of two lanes along the London-bound stretch of the A20 between the A260 and the M20 Junction 13.

Following an inspection of the bridge, damage was found to the parapet 15 metres after the Roundhill Tunnel.

A temporary safety barrier through the length of the tunnel is being installed tonight (Thursday).

A National Highways spokesman said: "For safety, the London bound A20 through the tunnel will be reduced to one lane until repairs are completed.

"Delays are expected during this time so people using the tunnel should plan ahead, leave extra time or seek an alternative route.

"When the tunnel is closed, eastbound diversions will be in place via A259 and A268 – drivers should follow the circle.

"Westbound diversions will be in place via the A268 and A259 – drivers should follow the square."

National Highways added that it had not been able to identify an incident that had originally caused the damage.