Roots: In the author's note, the author recommends The Gunpowder Plot by Alan Haynes as a more accurate account of what happened on 5th November 1605. There are references to the Scarlet Pimpernel, Tertullian, Nestorius, the Sword of Damocles, Lynda La Plante, and Mephistopheles.
Goofs: As the author's note points out, the book bears very little resemblance to historical events.
Dialogue Triumphs: 'You assumed I had the scrofula.'
'Eventually is a word that has no real meaning when you reach our time of life.'
The Doctor: 'I warn you, the reasoning power of my brain is phenomenal, yes, quite phenomenal.'
King James to 'Victor': 'You want to go to sleep, I want to go to sleep. We can both go to sleep together!'
And many, many more in undoubtedly the wittiest Missing Adventure.
Continuity: The Doctor and Vicki pose as pilgrims, the Doctor claiming to be a Doctor of Divinity sent from York Minster by the Bishop. Thanks to Vicki telling Hay under coercion that the Doctor travels though time and space, Hay assumes that he has control of her mind and is therefore a Grand Behemoth of the Supreme Order of the Rectangle (a warlock). The Doctor carries iron filings and has been conducting experiments with magnetos [possibly to educate Vicki - see below]. His eyesight is better than a human's, although he wears spectacles for reading. King James briefly considers offering him the position of Archbishop of Canterbury. He tells Vicki that pink octopi do not exist anywhere in the universe.
Barbara has always been fascinated by London in the Elizabethan and Jacobean eras. She worked at Hampstead High School for girls in 1952. She wears a green dress from the TARDIS wardrobe. Ian wears a grey hose and matching leggings. The Doctor provides them with a purse of silver coins appropriate to London 1605. Ian has adopted the Doctor's maxim of only killing when his own life is directly threatened (see The Dalek Invasion of Earth). The Doctor has explained to them that the TARDIS travels through the space-time vortex, since Ian refers to it by name. Ian has occasionally taken Barbara's history class when she has been off work due to illness.
Vicki wears a fur coat several sizes too big, which presumably comes from the TARDIS wardrobe. Later, she again dresses as a boy and dresses in a doublet and hose, adopting the name Victor (see The Crusade), and promptly becomes the object of the homosexual King James' affections. She had a full range of vaccinations injected by medical laser when she was five. She used to own a pony named Saracen. She has heard of d'Artagnan and the King James Bible but has only sketchy knowledge of the battle of Trafalgar. She has never heard of darts. She is reading a book on magnetos, which she borrowed, from the Doctor. Vicki has a fear of confinement.
The TARDIS is, of course, axe-proof and fireproof. The Doctor no longer has a spare key [he hasn't bothered to replace Susan's - see The Dalek Invasion of Earth].
Links: Ian recalls a couple of other occasions when the Doctor has claimed to have returned Ian and Barbara to their own time - these occasions include The Reign of Terror, Planet of Giants and The Dalek Invasion of Earth. Vicki recalls Rome (The Romans). The Doctor mentions Menoptera (The Web Planet) and Venusians (Venusian Lullaby).
Unrecorded Adventures: The Doctor claims to have had a hand in the design of the Privy Gardens, though he may be joking. He learned to carve fowl in the kitchens of the Tetrach of Phibbli, where sparrows are house-sized.
The Bottom Line: Simply marvellous. Roberts' use of wit is never better, giving The Plotters the same feel as The Myth Makers and The Romans, and the regulars are superbly characterised. The supporting characters, in particular the lecherous but likeable King James and the scheming Cecil also shine, resulting in arguably the finest Missing Adventure of the First Doctor.