‘Let’s get one thing straight: nobody knows us really.” So says June Gibbons of herself and her sister Jennifer early in this intriguing play based on the true story of the twin daughters of Caribbean immigrants. The point is, nobody was really allowed to know them. At a very young age, they turned their backs on the outside world and retreated into a place of their own, communicating with no one but each other. In 1986 journalist Marjorie Wallace wrote up their story — The Silent Twins — years before its tragic denouement, as discussed here last week.

The tale was perfect for dramatisation and for the sort of work done by the Shared Experience Theatre Company. Speechless — co-written by Polly Teale (who also directs) and Linda Brogan — covers the period bookended by the Queen’s Jubilee in 1977 (when the girls were 14) and Charles and Diana’s 1981 wedding and is primarily set in the girls’ bedroom, with a door that is rarely opened and then only by their mother and professionals trying to deal with them.

The play inevitably makes great demands on the two central actors, and Demi Oyediran (June) and Natasha Gordon (Jennifer, pictured) play the sisters with great sensitivity and an almost normal teenage angst that is quite remarkable, given that they are 29 and 35 respectively. Their mother Gloria (Anita Reynolds) is proud but beaten. Katie Lightfoot impressed in the dual roles of the twins’ headmistress and psychiatrist.

And then, shockingly, there is Kennedy (Alex Robertson) who, towards the end of the play, erupts into their room and has sex with both of them. The seeming brutality of the moment — although the sisters had wanted to lose their virginity, so it is not rape — nearly derails the subtlety of the play; but the incident did occur in real life, though not so dramatically.

It is extraordinary that, with work of this quality offered by Shared Experience, their core funding has been withdrawn by Arts Council England.