It was early 1969, I was 19 coming up on 20. I’d worked with the producer Tony Visconti that year on the Junior’s Eyes album. I was playing a Mellotron which was a relatively new instrument and difficult to keep in tune, but I’d found a crafty way. Tony asked: “How’d you do that?” and I said: “It’s just a fingering technique’’ and that was that.

Soon after, Tony called me up and said: “Rick, I need you to come up to London to play some Mellotron on David Bowie’s new single ‘Space Oddity’.” I drove up to London and parked on Wardour Street and went over to Trident Studios to meet David. “Tony says you can keep this bloody thing in tune,” he said. “Well yeah, hopefully,” I replied. It was before David was famous, so I wasn’t nervous about meeting him – it was just another bit of session work.

We knocked it out in about 20 minutes. I think it got to number five first time around in ’69 and then in ’75 when it was rereleased it went to number one. A year later David called and asked me if I’d play some piano on some new songs. So I went round to his house in Beckenham, Kent. I nicknamed it Beckenham Palace because at the time I was living in a tiny little terraced house in West Harrow and his kitchen was bigger than my entire place.

I sat at the piano while he played songs on his battered old guitar

Things had really changed for him. He was a successful artist and he had a young family. I sat at the piano while he played a load of songs to me on his battered old 12-string guitar. “Life on Mars” stuck out as being something very special. He wanted a piano solo, he wanted the album to be very piano-orientated. I was given complete freedom by him.

I’ve been asked many times if I thought it was going to be a great album, and the answer is yes. I know it’s very easy to say that in retrospect, but I’d been doing two or three sessions a day for the last three years – at that point, you can tell when you walk out of a session whether it’s going to do well or disappear without a trace. I remember telling people I’d just played on what was going to be a very iconic album – which Hunky Dory of course was.

On the same day I was asked to join the band Yes, David asked me if I wanted to form the Spiders from Mars, but as much as I loved David, I turned him down. He said I’d made the right choice, and he reiterated that on numerous occasions over the years. I heard later that he loved what I did on “Life on Mars”. He said it made the track, but that’s not true, the song made the track. The man was a genius.

Rick Wakeman’s new solo piano album Piano Portraits is released on 13 January