However, a number of these stories have been restored with new animated visuals accompanying the surviving soundtracks.

Speaking at a BFI screening of the latest animation, The Underwater Menace, executive producer Paul Hembury confirmed there are plans for more – indicating that the ambition is to complete the canon and cover off all of the missing stories.

“As long as there’s an audience out there who want to see them, then we will endeavour to continue,” Hembury said.

However, he cautioned:

“The DVD and Blu-ray market isn’t getting any bigger and it was a significant contributor to the financing that we used to make these, so it’s really incumbent upon us to say, ‘OK, if we’re going to be seeing less revenue from that source, we need to be able to replace it’ – and more, because our budgets have gone up pretty significantly. So we just need to be able to make it balance out.”

Despite confirming that at least one more animation is in the works, Hembury wouldn’t be drawn on which story was next on the slate, despite rumours that 1966 serial The Smugglers could be in the offing.

“I would love to be able to say yes – I can’t at this stage. We don’t have a five, 10-year plan to work through. We do them one at a time.  “In all truth, I don’t know whether we’ll ever get to a situation where we’ve done every one. [But] there is something coming.”

Hembury and The Underwater Menace animation director AnneMarie Walsh did however touch on how they decide which lost stories to animate, explaining that the selection process is “quite complicated” with the length of the stories, the quality of the surviving audio, and animated challenges posed by the story all being taken into account.

Of the 14 stories to be animated since 2006, 11 have been stories featuring Troughton’s Second Doctor, though Hembury and Walsh hinted that fans can expect more restorations featuring William Hartnell as the First Doctor in future.

“If we can keep going, then we will be a little more diverse in terms of the stories we select,” said Hembury.

“We weren’t necessarily trying to complete the [Troughton] series, but it made sense to do that as long as the sound was good enough and the stories made sense within the budgets we had and everything else,” added Walsh.

“But that doesn’t mean that we’re only going to do Troughton stories, or we’re going to do all the Troughton stories first. We are open to whatever makes sense.”

Doctor Who: The Underwater Menace is available on Blu-ray and DVD from 13th November.