Answer, Tubular Bells genius Mike Oldfield.
He provided the theme tune for all three.
Blue Peter, the perennial children's favourite commenced in 1958 and the show's theme has always been the tune Barnacle Bill, originally composed by Ashworth Hope (1880-1962) a solicitor turned musician. In 1979, Mike Oldfield appeared on the show and provided a version to show, in an educational film insert, how pop music was created via multi track recording techniques. His version proved so popular with viewers that the programme had it recorded to replace the Sidney Torch Orchestra rendition that had been its signature since the start, to be used as the theme tune for the next ten years.
Here is the original film
Oldfield released it as a single in November 1979 with the proceeds going to that year's Blue Peter Cambodia appeal. It reached number 9 in the UK charts.
And the song...
Pan's People dancing to it on Top Of The Pops 1979...
This was my era of Blue Peter. I have found memories of Peter Duncan, Simon Groom and of course, the divine Janet Ellis (later to become known as Sophie Ellis Bextor's mum)