Despite the fact that women make up roughly half of this planet’s population, it is an undeniable fact that the fairer sex are still largely neglected by the media. They may not always be missing: it may be that they are present but the vast majority of their clothes have gone missing, or – as the Bechdel test so neatly and depressingly points out – their entire emotional lives beyond their relationships with men have been misplaced. Whichever way you look at it, something is lacking, and it was so wonderful just to see three realistic, well-rounded female characters in Di and Viv and Rose that the sheer joy of it was almost distracted me from the play itself.

Of course, Amelia Bullmore’s three-hander is not so reductive as to see itself in these terms, as a play that is only about or for women: it is about people, people who make those first steps from adolescence into adulthood while living in each other’s pockets. The great strength of Di and Viv and Rose derives from the skill with which Bullmore captures the depth of a friendship that comes not only from growing up with somebody but from sharing a home with them, a home you have made together without your families for the very first time. Because, joyous as it is to see female friendships portrayed on stage, the real divide in this play is not between the genders, it is the difference between youth and age, innocence and experience, and it is played out by the cast with heart-breaking skill.

In the first half, set in the eighties, the eponymous characters meet in their university halls, and their blossoming friendships (or not) are portrayed in a series of quick snapshots which show hints of conversations and corridor meetings. The characters are defined quickly by the talented cast without feeling like stereotypes, they are simply believable, people whom any of us could have met: Anna Maxwell Martin’s middle-class and initially rather green Rose, who has never seen a microwave before and has a habit of putting her foot in it; Gina McKee’s academically driven Viv, with a rather dry wit and the dress sense of a WWII housewife; Tamzin Outhwaite’s kind, confident Di, who receives weekly care packages from the mother she loves but cannot bear to discuss her sexuality with. It does not matter that these students are being portrayed by actresses some decades older, in fact, it adds a certain awareness that no matter how time passes one is always essentially the same person.

The first half, which covers their three years at an unnamed university, is packed with humour and charm, and features a remarkable drunken dance sequence that drew spontaneous applause from the press night audience. It is slightly let down by a rather more predictable second half, preoccupied with the random tragedies of adulthood – but one cares so much for the characters by this point that it is difficult to think of it in such coldly evaluative terms. The audience watches them grow up together, and even in the darker moments of the play’s latter half, the performances are strong enough to carry us over a few excusable moments of cliché.

Also, the tone is generally kept light in spite of everything by the excellent sense of humour that runs through the whole play, shaping and characterising the characters’ friendships. They make each other laugh. They make the audience laugh. It is a joy to see female characters being allowed to be so funny.

It still may feel on one or two occasions as though too many calamities befall them, but I found it difficult to tell whether this feeling was a real critical judgement – a sense that it stretched credibility – or simply an emotional reaction, because I liked them all far too much to accept that their lives would not turn out exactly as planned.

After all, for the middle-aged members of the audience there will be a nostalgia in the scenes of eighties student-hood and brilliant imagined futures brought up against the harsh realities of life – but many of the readers of this website may perhaps experience a different emotion. After all, there is a strange sort of horror in seeing something not far removed from your own life in the play’s first half and then, in the second, this painful future: adulthood, with its truly adult decisions and endless struggle for happiness; the passing of youth that one knows is inevitable but would rather like to believe one can fend off.

Thanks to Bullmore, the cast and Anna Mackmin’s clever, unobtrusive and sometimes simply beautiful direction, Di and Viv and Rose does a wonderful job of holding a mirror up to certain kinds of friendships and certain kinds of youths. It would take a hard heart not to be moved to laughter or tears or both by this hilarious and rather lovely play.

Di and Viv and Rose is playing at the Hampstead Theatre until 23 February. For more information and tickets, see www.hampsteadtheatre.com/whats-on/2012/di-and-viv-and-rose/