Roots: The story is an adaptation of the Audio Visuals episode Vilgreth. Patrick Trethui (as in Professor) is a Nick Briggs pseudonym, having been used by him in directing his debut as the Doctor in the Audio Visuals story The Time Ravagers. The Hitchhiker's Guide to the Galaxy (giant spacecraft cleaning planets from space lanes) and the Star Trek episode 'The Doomsday Machine' (planet devouring space hulk). Roald Dahl's The BFG. The character of Vilgreth references the works of SF writer Philip Jose Farmer, specifically To Your Scattered Bodies Go, in the Riverworld series (which mentions Joe Miller, an eight-hundred-pound prehistoric 'titanthrop', a member of a pre-human race. He has a long, protruding nose and a lisp), and The Alley Man (whose protagonist thinks somewhat like Vilgreth, has violent rages and loves mechanical tinkering).
Goofs: Despite Vilgreth's ship's size being enough to consume an entire planet, and being dangerously close to Ormelia, its detonation nevertheless only has some debris harmlessly burn up in its atmosphere [that must have been one hell of a time bomb].
Technobabble: Bipolar vectoring modular flange jets and arc tunnel boosters are, apparently, what Vilgreth lives for.
Double Entendres: 'Spatial co-ordinates failure - what's that supposed to mean?'
'I am blighted with a sense of Justyce, Doctor' (okay, an Audio Visuals in-joke maybe)
'One of the deck hatches opened up and my ship fell into your hole.'
Dialogue Disasters: 'You cold-blooded lizard!'
Dialogue Triumphs: 'Chaarlk? This is no toime fer food'
Continuity: This story presumably takes place after the Doctor and Ace have parted company, and either before the seventh Doctor's experiences of 'The Sirens of Time' or between it and 'Doctor Who'. The Doctor has been promising himself a holiday and plans to visit the planet Ormelia, a favourite haunt in his 'younger days' (it's clearly been some time since, as he doesn't recognise the planet at first).
Ormelia has golden skies and undulating, pale green seas. It also has a force of Security Operatives (if Stelpor is native then we may also assume that the Ormelians are reptilian). Despite his familiarity with the planet, the Doctor has no idea how long a 'cycle' is [perhaps this isn't a standard Ormelian time unit and is specific to the time bombs their Security force use].
When Vilgreth asks the Doctor if he made the TARDIS, he says no, however he makes mention in his narration that 'technically indestructible' were words he saw in the design specifications for it [or perhaps for the type 40]. After exposure to the spaceship's furnace it suffers slight scorching to its outer shell configuration components.
Professor Patrick Trethui was among many things a scientist, traveller (he had a 'Jupiter run'), archaeologist and collector of spaceships, who [probably long] after the time of the 'Planet-eater' space craft period succesfully recovered remains of a Titanthrope in Devon. Using the DNA from the remains he recreated a living 'Titan', named Vilgreth. It is not indicated whether this name is native to the species - Vilgreth himself doesn't seem to be able to read, and prior to the professor fitting him with an electronic voicebox, he was without speech. The experiment was not entirely succesful, Vilgreth having headaches and violent moods, and when Trethui sought to sedate him with a dart gun, the Titan turned on his creator and killed him and the rest of the workers on his farm (save the housekeeper), fleeing in the Planet-eater craft, his favourite. At the time of the story Vilgreth is ten years old.
The Doctor drinks tea and takes either sugar or some other sweetener (the sound of stirring can be heard in the story's closing).
Untelevised Adventures: In his 'younger days' the Doctor regularly visited Ormelia.
Future History: Ten years previous to this story Earth's regions included Oceana and the European Senate (of which 'Old England' is part). 'Planet-eater' class space ships were built 'centuries' before the events of this story, but were decommissioned and mostly scrapped. Some however fell into the hands of museums and collectors.
Location: Vilgreth's Planet-eater spaceship, close to the planet Ormelia, [presumably] in the Milky Way Galaxy.
The Bottom Line: 'Rocks go in, flames come out. Burn, burn...'
If 'Last of the Titans' had been televised, perhaps the word of the day would be 'oddball'. Yet a sombre ending and an overall sense of doom prevents the story from fitting entirely within the mould of Season 24, one of its closest counterparts. Closer to 'The Pescatons', employing its half-narrative by the Doctor, it uses its single episode format well, and Nick Brigg's lumbering Vilgreth is an appealing and affecting supporting character.