The Welsh actor Philip Madoc has died aged 77, his agent said.
Madoc, who played the title role in the BBC drama The Life and Times of David Lloyd George, also appeared in shows including Doctor Who and The Last of the Mohicans.
His agent, Michael Hallet, said: "He passed away in hospital in Hertfordshire this morning after a short illness with his family around him. He will be hugely missed by everybody."
Madoc played a captured U-boat captain in an episode of Dad's Army in which he asked the names of his captors, prompting a furious Captain Mainwaring to shout the famous line: "Don't tell him, Pike."
The Merthyr Tydfil-born actor gained a reputation for playing villains, but insisted he did not mind. He said in one interview: "Certainly, initially I rarely played heroes because there was still this tradition that heroes were 6ft tall.
"Certainly if you had a voice that wasn't high and dark eyes then there was a feeling that you were set out to play the villains of this world. I didn't ever argue with that, because they were more or less the best parts."
The actor, who was divorced from the Hi-de-Hi! star Ruth Madoc, leaves two children and several grandchildren.