Despite its bleak premise – Sarah, revealed to be pregnant again, faces the prospect of losing her job and being cast out onto the streets – The Wages of Sin is an episode that if it isn’t quite played for laughs, certainly has a streak of mocking humour running throughout it.

This tone is established from the first scene in which Mrs Bridges (suspicious about Sarah’s sudden increase in appetite) leaps to the correct conclusion and brings in Mr Hudson to hear Sarah’s unwilling admission of guilt.

All three actors are given their chances to shine. Angela Baddeley makes the most of lines such as Mrs Bridges’ caustic summation of Sarah’s character (“You know, our Sarah reminds me of the Salvation Army banner. Thousands have been this way before, there is plenty of room for thousands more”).

Hudson, although he’s stern and foreboding after learning the news, can’t help but soften when Sarah apparently breaks down in tears (knowing Sarah’s passion for theatrically though, I have my doubts about how genuine her contrition is).

Pauline Collins gets most of the best lines as Sarah (desperate not to reveal that Thomas is the baby’s father) wildly extemporises under the withering glares of her two superiors and desperately cobbles together a rather unconvincing tale about how she was plied with drink and taken advantage of by a rich gent.

Collins’ performances across the series have been something of a mixed bag and so whilst I can’t confess to being that sorry to see the last of Sarah, at least she exits on a high.

As does John Alderton as Thomas, whose capacity for scheming remains finely tuned (although I do like the end of part two moment when it appears that he’s overplayed his hand and lost everything). If there’s any oddity with the script, then it’s slightly strange to end part one with Thomas refusing to acknowledge or help Sarah and then go straight into part two where he coolly ambles along to Mr Bellamy and asks for permission to marry the girl.

From Richard’s viewpoint this seems like the perfect solution, but later on, Lady Marjorie – returning home from aboard – is appalled when she hears the news. That she immediately counteracts his instructions makes it quite plain who wears the trousers at 165 Eaton Place.

Lady Marjorie’s harsh and ruthless streak bubbles to the surface as she tells Thomas that if he still wants to marry Sarah then both will have to leave their employ and as quickly as possible. This leaves him in a desperate position, but he has one last throw of the dice – a later brief meeting with Richard and Lady Marjorie in which he subtly raises the prospect of blackmail.

It doesn’t say a great deal for Richard (an MP, remember) that Thomas’ politely menacing words appear to have sailed right over his head. Luckily Lady Marjorie understands nuance a lot better than he does and sends the long-suffering Richard off to fix the problem.

Although last week money seemed a little tight, today that doesn’t seem to be a problem – Richard buys Thomas off with a £500 cheque (allowing the Welshman to realise his dream and buy a garage).

The episode then concludes with downstairs jollity as Thomas and Sarah celebrate their engagement – the festivities only slightly pausing when Richard and Lady Marjorie pop down to wish the couple well. There’s a delightful awkwardness in the scene from some of the servants to the arrival of their employers although eventually the party gets going again with a final reprise of ‘Uncle Albert’ – a song which has a very familiar tune ….

Although the episode opens in traditional style (an “oh Ruby” from Mrs Bridges) at the end Ruby actually gets something to do for once – revealing to Joan (Jane Carr) that she knows Thomas is the father of Sarah’s child.

Joan is another of those parlour maids who arrives from nowhere, but at least in her case there was a good reason. Christopher Beeney had been hospitalised after a motorcycle crash which occurred just before the recording of this episode, so all of Edward’s lines were given to this hastily created character.

So farewell Thomas and Sarah. They would later reappear in their own spin-off series, which didn’t last long and by all accounts was a far from happy production. Possibly when my UpDown odyssey has ended, it might be time to dig it out for a reevaluation.