BBC Radiophonic Workshop

BBC Radiophonic Workshop: The Alchemists Of Sound (2003)

The Delian Mode – Delia Derbyshire documentary

How Delia Derbyshire made her music

The enduring magic of the Radiophonic Workshop | Resident Advisor

Music Arcade – Radiophonic Workshop 3

From time 6:22 there’s a bit about creating the TARDIS sound effects. You can also
see a follow-up, below: