Apparently, it takes seven years to completely regenerate every cell in your body. So technically, you could say that seven years from now you’d be a completely different person. Theatre Bench’s Every Seven Years puts that theory to the test, following the relationship between Pam and Ralph over 63 years, from the ages of 21 to 84, stopping in with them at seven-year intervals. During that time, we see them fall in love, get married, have children, laugh, dance, argue, get drunk and grow old, experiencing together all the ups and downs that life brings with it.

I had high hopes for this play, part of Wimbledon’s Illuminate Festival, because the summary put me in mind of Patch of Blue’s Beans on Toast (part of last year’s Illuminate, coincidentally), which I loved; the two have a similar focus on memory and how it’s often the little moments that make a life what it is. And last night I left the New Wimbledon Studio – rapidly becoming one of my favourite fringe theatres – with the same warm fuzzy feeling I got from Beans.

Charlotte Baker and Ben Fensome, who wrote the show, play Pam and Ralph throughout their lives, subtly altering their appearance and body language with each new scene so that it becomes easy to forget these are two young actors playing octogenarians. They ride the emotional rollercoaster along with the audience, one minute laughing at each other’s accents (she doesn’t understand his Wiltshire slang any more than he gets her Geordie), the next coping with a crisis that threatens to end their marriage.

Director Scott Le Crass places the two inside a ring of cardboard boxes, from which they produce shopping bags, party hats and countless cups of tea (because, as we all know, there is no situation in life – good or bad – that can’t be improved by a nice cuppa). This simple design gives the play an unsettled feeling, as if Pam and Ralph’s lives are always on the verge of momentous change – which of course, in this play, they are.

The ingenious seven-year format was inspired in part by Granada Television’s Up series of documentaries, which has been following the lives of fourteen children since 1964 by returning to interview them every seven years. By just dropping in every once in a while, the play allows the audience to join the dots and decide for ourselves how its characters got from there to here.

The moments we share aren’t necessarily the big ones – we see Pam discover Ralph’s about to propose, for instance, but not the actual proposal, and there’s a lovely moment before her 50th birthday party when the two are alone, and she describes from memory every detail of his hands. Then again, life isn’t just about the big events; sometimes it’s about two 84-year-olds sitting in their kitchen in the middle of the night, drinking tea and reflecting on the years they’ve had together.

Every Seven Years invites us in to a love story that’s as messy as it is beautiful; neither Pam nor Ralph is perfect, but they’re perfect together. And the play is a heartwarming reminder that while a lot may change in seven years – events, circumstances, even our physical bodies – some things last forever.