AMY Herzog’s 4000 Miles could be described as an end-of-the-road story.

A cross-country bike journey culminates in 21-year-old Leo staying at the West Village apartment of his feisty 91-year-old grandmother Vera, played by Sara Kestelman.

Over the course of a month, as the mysterious events of Leo’s epic trip slowly emerge, a tender understanding develops between these unlikely roommates, allowing them to bridge the generation gap.

Vera is loosely based on Herzog’s own grandmother, Leepee, who sadly passed away shortly before the play had its UK premiere in Bath.

Kestelman never got to meet Leepee but did travel to New York before rehearsals began to see the building where she lived, which was remarkably just a couple of blocks from the actress’ own former apartment.

“She lived on West 10th Street in Greenwich Village, which is where I stayed when I was doing Peter Brook’s production of A Midsummer Night’s Dream in ’71,” she says.

“It’s incredible to think I might have passed this woman I would end up playing years later, in the supermarket.”

In the play, Kestelman says, Vera and Leo start out as a very old woman and a very young man but an ease and trust develops between them, allowing them to say things which might seem surprising across the generational gap.

As the drama develops, it becomes less clear who is meant to be more mature as the narrow line between growing up and growing old becomes somewhat tangled.

Kestelman is very close to her youngest godchild, with whom she regularly visits the theatre and art exhibitions.

“I know our relationship’s unique to us and we impart things to one another that only he and I know,” says the 68-year-old former Olivier Award winner.

“I think very often grandparents find it easier to talk to their grandchildren than they do to their own children because they have the distance of time and experience to lean on.

“That distance also makes it easier for grandchildren to say things to their grandparents they wouldn’t say to their parents.”

Kestelman and her fellow cast members only learned of Leepee’s death shortly before the production opened at Theatre Royal Bath, ahead of its transfer to Notting Hill’s The Print Room.

“We’ve dedicated the performances to her because without her we wouldn’t have this wonderful play,” she said.

“But the character of Vera has appeared in three of Amy’s plays and is central to her writing, which is heavily influenced by her family, so she may appear again.”

4000 Miles, directed by James Dacre, is at The Print Room, in Notting Hill, from Tuesday until June 1. Tickets, priced £20, are available at www.the-print-room.org or from 020 7221 6036.