Anyone passing Watford Palace Theatre this week may have heard a wailing coming from within. Tears have been in full flow during rehearsals for Ronald Harwood’s Equally Divided, a human comedy about doing the right thing.

“I felt about seven years old on occasions, stamping my foot and weeping hysterically,“ says actress Katharine Rogers. “It gets ridiculous, I’m losing the plot a bit because I’m getting so upset.

“It is tapping into quite deep emotional things, we get a bit teary and then I feel terribly self indulgent, and I think to myself oh god get a grip!“

The play is, Katharine assures me, a comedy. It follows two sisters who have returned to the family home, a converted railway carriage, following the death of their mother.

While Renata, played by Katharine, has lived a full life, with numerous husbands along the way, Edith has never left – remaining with their senile, difficult mother until the end. The trouble begins when it comes to distributing the family heirlooms.

“There’s a lot of bitterness and resentment between the two of them,“ says Katharine, “They’re as badly behaved as each other. They have messed up lives, they’re all slightly mad.

“The humour comes from the weaknesses of character and I think there’s a sense of when you’re this age, you really ought to be more grown up by now.“

Written by Oscar-nominated playwright Ronald Harwood, the play also stars Beverley Klein, Gregory Gudgeon and Walter Van Dyk.

“It’s very funny, but it’s very emotional as well,“ adds Katharine. “It’s about 50-somethings, about parents dying and disappointed lives, about not having achieved quite what you wanted to achieve. It’s a rather extraordinary play. On first reading it seems to be one thing and as you go into it it becomes a different thing entirely.“

Equally Divided is at Watford Palace Theatre until February 23. Details: 01923 235455