Basil, who runs the titular hotel in Torquay, is a misanthropic, pessimistic man who is desperate to belong to a higher social class. He sees the successful running of the hotel as a means of achieving this dream, yet his job requires him to be pleasant to people he despises. His unstoppable wife Sybil will often get in the way of Basil's treatment towards the guests, often trying to bridge the peace, or pick up the pieces, to quite limited success.
The episode "Communication Problems" establishes that he is from Swanage.
Basil has staunch right-wing views regarding almost everything he comes across. This is especially apparent in "The Wedding Party", when he shows open disgust towards a young unmarried couple with an active sex life.
He is terrified of his wife's sharp tongue, but wishes to stand up to her, and his plans often conflict with hers. She is often verbally abusive towards him (describing him as "an ageing, brilliantined stick insect") and though he is much taller than Sybil, he often finds himself on the receiving end of her temper, expressed verbally or physically. Despite being terrified of his wife, Basil manages to gain the upper hand on one occasion. During "The Kipper and the Corpse", Sybil refuses to help Basil dispose of the body of recently deceased guest Mr. Leeman. Basil gains his revenge towards the end of the episode, when he asks a number of disgruntled guests to direct their complaints towards Sybil. In "The Psychiatrist", he has a row with Sybil during which he calls his wife a 'rancorous, coiffured old cow'.
Basil takes many of his frustrations out on the hapless Manuel, physically abusing and bullying him in a variety of ways. On occasions he also assaults others, such as strangling the guest Mr. Hutchinson in "The Hotel Inspectors", kneeing Major Gowen in "Basil the Rat", 'accidentally' elbowing a young boy in the head in "Gourmet Night" and, in the same episode, famously striking his "vicious bastard" of a car with a tree branch when it refuses to move.
Another eccentricity affecting Basil is that of occasionally swapping words around in a sentence while propounding a falsehood, for instance in "The Anniversary" when he announces to the party guests that it's "perfectly Sybil! Simple's not well. She's lost her throat and her voice hurts", and – less obviously – reassuring himself as much as his wife in "The Wedding Party" that the sound of knocking on his bedroom door was "probably some key who forgot the guest for their door". He also has difficulty disconnecting his thought-process from unrelated events, as in "The Wedding Party", when he is looking through Polly's sketchbook of life-drawing pictures and answers the telephone with, "Hello, Fawlty Titties?" or in "The Psychiatrist", where, after inadvertently staining the chest area of a female guest with paint, he realises that Sybil has noticed, but then in confusion puts his hands all over the guest's breasts as a means of stopping her from seeing it.
Basil is known to have served in the British Army during the Korean War, possibly as part of his National Service. He claims: "I fought in the Korean War, you know, I killed four men" to which his wife jokingly replies, "He was in the Catering Corps; he used to poison them". He is often seen wearing a military tie, and a military-type moustache. He also claims to have sustained a shrapnel injury to his leg in the Korean War, which has a tendency to flare up at convenient moments – usually when Sybil asks him an awkward question. (In fact John Cleese was only 13 years old when the Korean War ended.)
John Cleese himself described Basil as thinking that he could run a first-rate hotel if he didn't have all the guests getting in the way. He has also made the point that on account of Basil's inner need to conflict with his wife's wishes, "Basil couldn't be Basil if he didn't have Sybil".
Basil seems to have an attachment to any upper-class guests visiting, such as Lord Melbury (who turned out to be an impostor), Mrs Peignoir (a wealthy French antique dealer) and Major Gowen, a recurring war veteran, although Basil is sometimes scathing towards him, frequently alluding to his senility and his attachment to the bar ("drunken old sod"). He has particular respect for doctors, having aspired to be one himself, and shows a reverential attitude to Dr. Abbott in "The Psychiatrist" (until he learns that Dr. Abbott is a psychiatrist), and Dr. Price in "The Kipper and the Corpse" (until Dr. Price begins to ask awkward questions about the death of Mr. Leeman, and inconveniently requests sausages for breakfast).
Basil is constantly intimidating guests, and liable to pick up a tail-end of a situation and turn it into a farcical misunderstanding. Basil is known for his tight-fisted mannerisms, employing incompetent builder O'Reilly in "The Builders" because he was cheap. Notoriously, he also becomes indignant whenever a guest makes a request, even if the request is quite reasonable. In "The Kipper and the Corpse", he was put out when a sickly guest politely asked for breakfast in bed, and Basil sneeringly went so far as to ask him which wood he would like his breakfast tray made out of.
Basil has been married to Sybil since 1962, as stated in "The Anniversary". He very rarely shows any signs of real love for his long-suffering wife ("my little piranha-fish" is one of the kindest epithets he bestows on her), and vice versa (In "The Wedding Party", they are shown to sleep in separate beds). Sybil's friend Audrey (an unseen character, with the exception of "The Anniversary") is often the only support she gets. Ironically, "The Anniversary" is one of the few episodes in which Basil tries to be nice to Sybil, who misreads the situation and believes he has forgotten their anniversary.
John Cleese reprised the role of Basil in the song "Don't Mention the War", based on the situation in the episode "The Germans", for the 2006 Germany FIFA World Cup. This same phrase, "Don't Mention the War", was used as the title of the first episode of a 5-part BBC documentary series When Rover Met BMW.