A Hillman Imp car is seen in two scenes with son Dennis Wilson shortly after 4th April 1963 but the car was not launched until a month later on 3rd May 1963.
Dennis Wilson threatens Mrs Wilson with revealing her bigamy, which he says is an offence on her part, even though her husband was the bigamist, not her. However, if it could be proven that both partners knew the second marriage was bigamous at the time it occurred, then both of the partners may be open to prosecution under the bigamy laws.
In the opening scene, Alice is seen typing. She is using a large, light brown typewriter with cream-coloured keys. Cut to a close-up of her hands at work and the machine is a smaller one that is black with black keys.
The major is always shown with a beard. British army officers ( unlike naval officers) were not permitted to have beards while in uniform. Covert operatives often had beards while under over, in some assignment, but not in London, in uniform. Applies to all episodes.
Southsea (and the whole of Portsea Island) is fairly flat. The burial scene on a hill with views of the sea was clearly not shot in Southsea.
In flashbacks to the war, Alexander Wilson is shown to be a British Army officer. But he has a beard. This would not have been permitted.