Went to see this play at the National. It was orginally written for radio and not sure it really worked well on stage. Have read Lyn Gardner's review in the Guardian which made me chuckle. Have copied this below.
Flora and Edward are breakfasting in the garden. A wasp flies into the marmalade, a sting in what appears to be paradise. The campaign to kill it is mounted by Edward with military precision and a polite middle-class ruthlessness. But it is Flora and Edward's marriage that is dying, and the end is hastened by the stranger at the gate, a match seller who has apparently been there for months.
Harold Pinter's 1958 play was conceived for radio, and that is where it should have stayed. Iqbal Khan's revival is perfectly serviceable, and Pinter's script has flights of lyric fancy, but staging A Slight Ache destroys its nagging power, and what is mysterious becomes spelled out. The ancient Greek playwrights knew the appalling power of not showing the thing we fear most, and I reckon that Pinter does, too. On radio, the audience never knows whether the match seller really exists or if he is a figment of the couple's imaginations. On stage we can see him, and he looks like someone on his way to a party hosted by Max Mosley. The result is banal. A Slight Ache is transformed from a play about metaphysical and emotional crisis into a play about a couple of Daily Telegraph readers concerned about people loitering with intent.
Clare Higgins and Simon Russell Beale are perfectly fine, better than their material, and Jamie Beamish is quietly menacing, but the overall effect is slight, and can be batted away like a wasp.
http://www.guardian.co.uk/stage/2008/jul/30/theatre