I believe I do have a timeline of events that you might find illuminating.
Gally informs her parents, Patrick and Lettie, about the plans that she and Susanna have to tour the country as a musical act.
Her parents are hesitant, but are somewhat reassured when Gally tells them that Susanna has recently married a Captain Noone and that he will be travelling with them.
Gally’s brother, Newt, has been on the sidelines of the discussion. When their parents withdraw to discuss the matter, Newt asks Gally more questions about Susanna’s supposed husband.
Newt deduces that Captain Noone is a ruse. He tells Gally that the play on words with ‘no-one’ is not as subtle as she might think it is.
Gally tells him that it is too late to change the name from Noone, not least because she and Susanna are planning to rename their act ‘Midnight & Noone’.
The two discuss Gally’s new stage name of Midnight, agreeing that it is better suited than Nightingale given Gally’s low voice. This gives Newt an idea for a song in which Gally would play the part of a man who impersonates birds.
Gally warns her brother, Newt, that she has a “super colossal” favour to ask him.
Through cryptic references to Susanna’s pretend husband, Major Noone, Gally asks if Newt would father a child with Susanna, which Gally and Susanna could then raise together.
Newt is reluctant to do so. In his life generally, Newt has no interest in the required activity and never intends to try it. He remarks that there are other ways of achieving the same effect.
At this point, Gally begins to speak more plainly. She had particularly hoped that Newt would do this for them, so that the kid would be the closest possible thing to being Gally’s own child.
This convinces Newt and they agree to the plan. He asks to be part of the child’s life in the role of an uncle.
Gally begins to explain the practicalities of the arrangement by asking if Newt knows Crewe.
Newt knocks on the door of a hotel room. Susanna opens the door and greets him by saying: “Mr. Noone, I presume.”
Susanna thanks Newt for “filling in” and goes on to say: “I’m terribly sorry about breaking your duck.”
Despite not usually drinking, Newt takes a swig from a hip flask that Susanna has brought, since she points out to him that it is “rather a day for doing things you don’t do”.
They exchange awkward, but affectionate, conversation as they mentally prepare themselves for what they came to do.
Vanessa is speaking to members of her new sewing circle. They offer her their condolences on the death of her mother.
It transpires that there is some confusion in the group about the identity of Vanessa’s mother.
Vanessa tells them that her mother was Susanna Noone, who had died three years previous from a long illness.
The sewing circle members had been under the impression that Gally Nightingale was her mother, who had died only three weeks previous in a bombing.
Vanessa explains that Aunt Gally, as she calls her, was her mother’s companion. She tells them that, although Gally was like a second mother to her, they were not related.
The group are surprised to learn this, given Vanessa’s resemblance to Gally.
While sharing a drink, Vanessa asks Uncle Newt questions about her parentage. She had put off asking the questions before now, even though she had her doubts for a while.
Uncle Newt is able to tell her that Susanna Noone was indeed her mother, despite Vanessa’s resemblance to Aunt Gally.
He does go on to say that Gally would have loved to have been Vanessa’s mother, and that, really, she was one of her two mothers in every meaningful sense.
When Vanessa asks what her father looked liked, Newt only says that he never met Major Noone.