Network Rail has apologised for the day of delays and train cancellations on services through Watford Junction after damaged brickwork in a tunnel on the station approach.

The company said most services are returning to normal this afternoon but could be subject to some alterations or cancellations for the remainder of the day.

Passengers are advised to check before they travel for the latest information.

Sam Kelly, Network Rail spokesman, said: "We are sorry for any delays this morning owing to problems at Watford tunnel.

"Passengers are advised to check with their train operator or National Rail Enquiries for the latest travel information."

The damage was discovered in a routine overnight maintenance inspection.

A 20mph speed restriction is in place through the tunnel, meaning there were a number of service alterations this morning.

Engineers are due to carry out further work tonight and throughout the rest of the week.