Here Come The Double Deckers - theme tune

Here Come The Double Deckers was a children's programme from the early 1970s. I remember it well - more so for the song and the character called Brains. It was a combined British/American production that only run for seventeen episodes. It was scheduled for more episodes but was terminated before the full production itinerary could be completed. 

It was about a group of seven children who had a secret den on a double decker bus inside a junk yard.