The Railway Children Return costume designer Dinah Collin on creating period looks for Sheridan Smith, Jenny Agutter and the child stars

“Before you know about the cast, there has to be a consultation with the producer and director about the aim,” she says. “In this case, it was very clear that it had to look real – you had to believe where they were and the time they were in.”

The film is set in Yorkshire in the 1940s. “But the clothes very likely would have been hand-me-downs from the late ‘30s, before the war,” she says.

A spotted dress worn by young actor Beau Gadston, as Lily, was made using a piece of original fabric given to Dinah by a friend. “We could only get one dress out of this, so we had to get a company to photograph it and print it mechanically,” she says.

“We made various pieces for our main cast, like the knitwear and the dungarees for the middle ones, and things we needed doubles for.”

Doubles are needed because of child working hours, which mean the principals have stand-ins who need identical clothing.

“Shooting when we were in May/June, you couldn’t be certain of the weather, hence the layers,” Dinah says, adding: “Having to create this knitwear gave us an opportunity to give them a strong individuality.”

Period costume research is easier now than it was before period photography could be found online. Most of the clothes come from costume houses, chiefly Cosprop and Movietone Frocks.

For the fittings, the child actors and their parents went to Cosprop in London. “The director Morgan came as well to the early fittings, which is very nice, because then you have got this whole building process,” Dinah says. “It’s a sort of trying on, not a definite ‘this is it’.

“It’s definitely a clue to the character for the actor,” she says. “The moment when you put the children into the clothes gives them an idea about what the whole thing might feel like, and that is terribly important.”

This happens early in production. “It’s quite a process,” Dinah says. “You have got to get them soon enough so that, if you have got to make something, you have got time.”

Jenny Agutter reprises her role as Bobbi, but without her Tam O’Shanter. This time, she gets a beret. “She is beautiful. She wears trousers, which I think is really lovely,” Dinah says.

Sheridan Smith plays her daughter. “Sheridan was lovely. She is very funny,” says Dinah. “As a headmistress, she wears a slightly tweedy suit. And there’s a green cord jacket. That’s an original jacket that I put on her because it gives her a marvellous waist, and it’s not too country or smart looking. She has dungarees, too.”

Dinah’s roll call of costume design credits is lengthy and impressive. In 1996 she won a BAFTA and an Emmy for Pride and Prejudice (the Colin Firth and Jennifer Ehle BBC TV version), and the BAFTA Cymru award for Gwen in 2019, starring Maxine Peake.

A recent favourite film she has worked on is The Duke, with Jim Broadbent and Helen Mirren, which was filmed in Yorkshire and also stars Austin Haynes, the young Yorkshire actor who now features in The Railway Children Return.

Dinah dressed Matt Damon for The Bourne Supremacy in 2006. She says: “I went to Prague from Berlin with a bundle of coats – the sort of little dark business coat that everybody was wearing then – and I found one that worked, and we could buy it in multiples. He was very pleased.”

When not jet-setting and train-hopping, Dinah lives near Brighton. “I never really had any formal training,” she says. “The trick is to know who is really good at doing what you need.

“I did illustration and graphic design at was the Central School In Holborn. It became central St Martin’s later. I never really enjoyed it. I came from Cambridge Art School to London, and it was all grey, in 1960. I wanted to move to the Theatre department, because I lived in a house in Notting Hill – it wasn’t grand like it is now – with a theatre designer and a painter. They didn’t want me to move courses, so when I left, I wrote to repertory theatres and offered to paint sets. Then I found out about wardrobe departments and vintage clothes.”

She met John Bright, who established Cosprop in 1965 and is a costume designer himself, an Academy Award winner for Merchant Ivory’s Room with a View. At first, Dinah says, he bought genuine vintage clothes to loan but realised they should be kept as an archive and as templates for designers to use and copy.

“For me, the life I have had, and am having, is all about all the relationships you build up over time,” she says.

At the end of the 1960s, she went to work for the BBC, working on Howard’s End with Glenda Jackson. “I stayed for about two years and then I left – I’ve got four children. I went back at the end of the 1970s and worked on contract.”

For The Railway Children Return, Dinah had the help of some of the Gentleman Jack wardrobe team. “I can’t tell you how marvellous they were,” she says. “We had a church hall in Haworth where we did all the background fittings. I was so grateful to have such experienced, lovely people. It’s like a big family.”

She will be going to see the film with her own grandchildren. “It’s quite good to see it more than once,” she says. “Then you can be a viewer, rather than a person who worked on it. Otherwise, you are very conscious of the process that you have been through to get it there.”