Character: Captain Halliday
Actor: Philip Franks
Episode: Bad Blood

Philip Franks had a great time playing a ruthless biological warfare researcher in Foyle's War.

"Captain Halliday is part of a secretive group doing research into germ warfare. He's completely cold-blooded, doing what a squeamish non-combatant would never do. But his philosophy is pragmatic - he knows that at any time the Germans could be there ahead of us. So he has to prepare germ warfare plans in the understanding that we might as well get in first.

"He knows that it is not good to experiment with other human beings, but lives across the whole country could be at stake. Germ warfare was extremely ugly but it had to be done. It was just lucky that events overtook it and it was never used."

Captain Halliday's experiments do not impress Foyle (Michael Kitchen) when they lead to Sam (Honeysuckle Weeks) falling critically ill.

"Foyle sees in Halliday a dangerous fanatic but when Halliday looks in the mirror he sees he has a job to do, even though they are making it up as they go along. On the face of it he is your worst enemy but he is actually trying to save the world.

"When Foyle criticises him, the fact that Halliday is in uniform means he can shout back. It does give you a feeling of authority and a different stance and it's very easy to feel better in the uniform. It was a good change for me to play fish-eyed and cold."

Adds Philip: "I'm a great fan of Foyle's War and my favourite character is Sam. My only regret is that I didn't get to meet Honeysuckle and my tinkering with anthrax put her in a coma! I think she is brilliant and I hope she survives my meddling."

Philip has spent most of the last year in uniform - he has also played a First World War soldier in the play Journey's End.

"It was a brilliant production but in the summer, the heavy uniform was unbearable. I sweated on that, but on Foyle's War I was glad of the uniform filming out on Seven Sisters, where it was a bit windswept. We were there in the middle of an old fortification looking down on an evil experiment on poor sheep. It was stunning scenery but I think we spooked a few passing joggers!"

Philip is best known for his role as Charley in The Darling Buds of May. "Everyone remembers it and the cable box gives you a picture of Dorian Grey every day. So you get to stay young when the real you is going grey and saggy!"

He also played Sergeant Craddock in Heartbeat for four years and his other credits include Martin Chuzzlewit, The Buddha of Suburbia and The Green Man. Philip has also directed Mary Shelley's Frankenstein at the National Theatre and The Tempest at the Liverpool Playhouse.