David Morrissey has revealed how the extras in new drama The 7.39 became like bodyguards as they filmed on location at Waterloo station.

The Walking Dead actor stars with Sheridan Smith and Olivia Colman in the BBC show about a married man who falls for a young woman he meets on his daily commute.

The two-part drama, written by David Nicholls of One Day and Starter For 10 fame, was filmed in several busy public locations in London as well as on a moving train.

Morrissey revealed: "Because the supporting artists were all in our carriage all the time, we got to know them. We did those journeys on the train every Sunday and they became like part of the team. So when we got to film at Waterloo Station they had more jobs to do than just be supporting artists.

"They had to wrangle people who were entering the shot, they were able to engage them in conversation. They really were brilliant, they would surround Sheridan and I and Olivia as we were doing the scenes. They were pretending to be background people but they were actually also wranglers - there to ward off anybody who was there."

But Smith admitted their extras had not always been able to shield them from members of the public who got carried away when they spotted the camera. She said: "Because it's about the commute, and about people going to 9 to 5 jobs, we had to do it in Waterloo when it was real rush hour.

"So you'd get lots of out-takes of football fans piling off trains and going 'Wahay!' and piling in front of the camera. But it made it more real and it was a lot of fun and it's a great story."

The actress added: "It's a bit steamy, I'm a bit nervous about my mum and dad seeing it, to be honest, but David's gorgeous so I wasn't complaining."

Morrissey admitted he has never really experienced a long-term commute to one job, but filming the drama on a moving train became like one.

He revealed: "It was a commute, we jumped on the train and went to a station about an hour and a half from London, and then we got off and had a coffee and then turned around and went the other way and we did that quite a number of times during our day for a month of Sundays.

"One carriage was our dressing room and then another was where we hung out. We had one whole train to do all the story in. Both day and night we were filming on the moving train, it was crazy."

:: The 7.39 begins on Monday January 6 at 9pm on BBC1.