He worked on the show from 1984–2003.
He first worked as a puppet-maker on Gerry Anderson shows such as "Joe 90", "Captain Scarlet", and "Thunderbirds" before founding Clearwater Features with Robert D. Cardona in 1983.
Mitton wrote six episodes of "TUGS" and directed nine of them. When Clearwater Features closed down in 1990, he joined the Britt Allcroft Company.
Although some episodes were based on Railway Series books, some of the script was written by him and Britt Allcroft. After the death of the Reverend W. Awdry in 1997, Mitton and Allcroft decided to create stories of their own. He provided stories for episodes of the sixth and seventh seasons. His last episode as writer was Edward the Very Useful Engine, but he continued as director until Three Cheers for Thomas before retiring. Steve Asquith replaced him as director from then on. David was also a model unit creative consultant for Thomas and the Magic Railroad.
He was working with Gerry Anderson producer David Lane with their own company "Pineapple Squared Entertainment", which was due to launch a new CGI Animation series "Adventures On Orsum Island". Only a few episodes of "Orsum" were semi-completed before his death.
David Mitton suffered a heart attack and died on 16 May 2008, at the age of 69. His death was not announced until 28 May 2008. Many "Thomas the Tank Engine" and "TUGS" fans were greatly saddened by this news.
Both episodes were co-written with Britt Allcroft.
- Rusty to the Rescue (co-written with Britt Allcroft)
All episodes are co-written with Britt Allcroft and nine episodes were co-written with Allcroft and David Maidment.
- Cranky Bugs
- Horrid Lorry
- A Better View for Gordon (with Allcroft and Maidment)
- Lady Hatt's Birthday Party (with Allcroft and Maidment)
- James and the Trouble with Trees (with Allcroft and Maidment)
- Gordon and the Gremlin (with Allcroft and Maidment)
- Bye George!
- Baa! (Allcroft and Maidment)
- Put Upon Percy
- Toby and the Flood
- Haunted Henry (with Allcroft and Maidment)
- Double Teething Troubles (with Allcroft and Maidment)
- Stepney Gets Lost
- Toby's Discovery
- Something in the Air
- Thomas, Percy and Old Slowcoach
- Oliver's Find
- Happy Ever After
- Sir Topham Hatt's Holiday
- A Surprise for Percy
- Make Someone Happy
- Busy Going Backwards (with Allcroft and Maidment)
- Duncan Gets Spooked (with Allcroft and Maidment)
- Rusty and the Boulder
- A Bad Day for Harold the Helicopter (story concept)
- The Fogman (story idea)
- It's Only Snow (story idea)
- The World's Strongest Engine (story idea)
- Scaredy Engines (story idea)
- Percy and the Haunted Mine (story idea)
- Middle Engine (story idea)
- James and the Red Balloon (story line)
- Jack Frost (story idea)
- Gordon Takes a Tumble (story idea)
- Percy's Chocolate Crunch (story idea)
- Thomas, Percy and the Squeak (story idea)
- Thomas the Jet Engine (story idea)
- Edward the Very Useful Engine
- Rusty Saves the Day (story idea)
- Toby's Windmill (story idea)
Awards and nominations
- Nominated - British Academy of Film and Television Arts - Best Animated Film for "Thomas The Tank Engine & Friends", 1985, shared with Britt Allcroft and Robert D. Cardona; 1987 shared with Robert D. Cardona.
- Teresa Gallagher, Rasmus Hardiker, William Hope and David Menkin would soon become voice actors on the fiftieth anniversary reboot of the original Thunderbirds series, the latter which David Mitton worked on.
- Martin Sherman worked as a voice actor on David's unfinished "Adventures on Orsum Island".