The most successful talent-spotting show of all time
Opportunity Knocks was first launched on BBC radio in 1949 when it gave a lift up the ladder to the likes of Spike Milligan and Frankie Vaughan.
On television between 1956 and 1977, it produced acts of the calibre of Bonnie Langford, Lena Zavaroni, Les Dawson, Freddie Starr, Su Pollard, Frank Carson and Little and Large.
It was the most successful talent-spotting show ever and 10,000 acts were auditioned each year but just 175 got their chance to appear on the box.
Hughie Green hosted the television version on ITV until 1978 before the show was revived on the BBC in the late 1980s with Bob Monkhouse and Les Dawson.
The winning acts on Opportunity Knocks were decided by the viewing public.
In the ITV version this took the form of a postal vote, the winner of which was announced the following week.
The BBC revival was notable for being the first TV show to decide its winner using the now-standard method of a telephone vote.