William Arnold Ridley was born in Walcot, Bath, Somerset, England, the son of Rosa Caroline Morrish (1870-1956) and William Robert Ridley (1871-1931). His father was a gymnastics instructor and ran a boot and shoe shop. He attended the Clarendon School and the Bath City Secondary School where he was a keen sportsman. A graduate of the University of Bristol, he studied at the Education Department, and played Hamlet in a student production. Ridley undertook teaching practice at an Elementary School in Bristol.
Ridley was a student teacher and had made his theatrical debut in Prunella at the Theatre Royal, Bristol, when he volunteered for British Army service in August 1914, upon the outbreak of the First World War. He was rejected due to a toe injury, but in 1915 was able to enlist as a private in the Somerset Light Infantry. He saw active service in the war, sustaining several serious injuries: his left hand was left virtually useless by injuries sustained on the Somme; his legs were riddled with shrapnel; he was bayonetted in the groin; and the legacy of a blow to the head by a German soldier's rifle butt left him prone to blackouts. He was medically discharged from the army with the rank of captain.
Having unsuccessfully attempted to establish a film company between the wars, Ridley rejoined the army in 1939, following the outbreak of the Second World War. He was commissioned into the General List on 7 October 1939 as a second lieutenant and was given the service number 103663. He served with the British Expeditionary Force in France during the "Phoney War", employed as a "Conducting Officer" tasked with supervising journalists who were visiting the front line. In May 1940, Ridley returned to Britain on the grossly overcrowded destroyer HMS Vimera, which was the last British ship to escape from the harbour during the Battle of Boulogne. Shortly afterwards, he was discharged on health grounds. He relinquished his commission as a captain on 1 June 1940. He subsequently joined the Home Guard in his home town of Caterham, and ENSA with which he toured the country. He described his wartime experiences in Desert Island Discs in 1973.
After his medical discharge in 1916, Ridley went into acting. In 1918, he joined Birmingham Repertory Theatre, staying for two years and playing 40 parts, before moving on to Plymouth, where he eventually had a break from the stage when his war injuries began to trouble him.
After being stranded for an evening at Mangotsfield railway station, near Bristol, Ridley was inspired to write the play The Ghost Train (1923). It was a tale of passengers stranded at a haunted railway station in Cornwall, with one of the characters being a detective trying to catch smugglers. The show became a huge success, enjoying 665 performances in London's West End and two revivals. The Ghost Train was first filmed in 1931 and again in 1941 when it starred Arthur Askey. Ridley also wrote more than 30 other plays including The Wrecker (1924), Keepers of Youth (1929), The Flying Fool (1929) and Recipe for Murder (1932).
During his time in military service in the Second World War he adapted the Agatha Christie novel Peril at End House into a West End play that premiered in 1940. Ridley's post-war play, Beggar My Neighbour, was first performed in 1951 and adapted for the Ealing Comedy film Meet Mr. Lucifer (1953).
Ridley worked regularly as an actor, including an appearance in the British comedy Crooks in Cloisters (1964). He also played Doughy Hood, the village baker, in the radio soap opera The Archers and the Rev. Guy Atkins in the ITV soap Crossroads from the programme's inception in 1964 until 1968. However, he became a household name only after he was cast as Private Godfrey, the gentle platoon medic in the popular British comedy Dad's Army (1968–1977). He continued to appear into his 80s, and was appointed an OBE in the 1982 Queen's New Year Honours List, for services to the theatre.
He was manager of the Leas Pavilion Theatre in Folkestone in the 1970s, writing, directing and producing a number of plays for the rep company based there.
He was the subject of This Is Your Life in 1976 when he was surprised by Eamonn Andrews at London’s Marylebone Station.The Wrecker (1927)
The Ghost Train (1927)
Old Leeds (1928)
Keepers of Youth (1929) (filmed in 1931)
Third Time Lucky (1932)
Half a Crown (1934)
Recipe for Murder (1936)
Peril at End House (1945, from Agatha Christie novel)
Easy Money (1948)
East of Ludgate Hill (1950)
Murder Happens (1951)
The Return (1953)
Mrs Tredruthan's Son (1953)
Beggar My Neighbour (1953)
You, My Guests (1956)
Hercule Poirot Strikes (1967, from Agatha Christie novel)
Ridley was married three times. His first marriage lasted from January 1926 to 1939, and was followed by a short marriage beginning in 1939 before his final marriage to actress Althea Parker (1911–2001) on 3 October 1945; they had one son, Nicolas (b 1947). Ridley died in hospital in Northwood in 1984 at the age of 88 after falling at his residence in Denville Hall, a home for retired actors. He was cremated at the Golders Green Crematorium and his urn buried at his parents' grave in Bath Abbey Cemetery. His collection of theatrical memorabilia was left to the University of Bristol and has been made available online.
He was a Freemason, and belonged to the Savage Club Lodge in London.
He was the great-uncle of actress Daisy Ridley, who played Rey in Star Wars: The Force Awakens.