5 days in the life of Cathy Shipton

Monday: Six days to the London Marathon. Out of bed and running before I have time to think: just me, the herons and a couple of scullers on the river. I pushed hard yesterday, doing 12 miles in 1hr 29min - a personal best - I just wanted to go for it and felt strong. Rehearsals at 2pm today which feels like a luxury: I manage to do lines and get my life in some kind of order. I'm rehearsing Steaming, a bawdy, raucous and moving piece by Nell Dunn. We all gather after lunch in good spirits despite the fact that two of the cast have rotten colds. I make a mental note to take more vitamin C and zinc - I can't succumb to a cold at this stage. Oh, the hypochondria of the long-distance runner.

TUESDAY: To focus on the race next Sunday it is vital to keep this week as normal and uncluttered as possible ... some hope. I am called at short notice to appear on Channel 5's Live and Dangerous to plug my book Marathon Manual and chat about running and life - but at 1.10am!

Not running today as part of the wind-down, but I now feel normal only in my kit and I'm terrified I'll forget to run. Feel twitchy as I spy three strong runners pacing out along the South Bank - they can't be running on Sunday, can they?

Rehearsals are productive. Home for supper and Chris, my partner and fellow runner, has prepared vegetarian lasagne and apricot and apple crumble, stoking up the carbohydrates.

We celebrate like mad things before I leave for the studio as Fulham have secured promotion to Division Two. (Chris is running to raise money for Fulham 2000 - to keep Fulham at Craven Cottage.)

I enjoy Live and Dangerous: the hosts are laid-back but bright, and it's thrilling being whisked off home at 2am.

WEDNESDAY: Wake feeling foul and not as jolly as last night. Late for rehearsals and resist running for fear of twisting my ankle (weak ankles are my Achilles heel). My dad had weak ankles, too; it must run in the family. Dad is the reason I run. He died 12 years ago from heart disease, as did his father and grandfather before him, and when I got Casualty, I offered my services to the British Heart Foundation. I have run three London marathons and this year will be heading up a 1,000-strong team of heart runners, many of whom suffer from heart problems.

Walking over Hungerford Bridge I look down the Embankment, the last mile of the run, and am reminded of a woman I ran behind last year. Emblazoned on the back of her T-shirt was "This one's for you, Dad". That got me through the last difficult miles.

THURSDAY: Today looks like it's going to be the most normal day of the week. We run most of Act One without scripts. It's great seeing the characters develop. Outside it is warming up, which doesn't bode well for Sunday.

I find myself scanning long-range weather forecasts in papers and on Ceefax - obsessed? Moi? Apparently it will be 16C and partially cloudy. Hydration will be important.

I've started "snacking" between meals, bananas and oat bars mainly, much to the annoyance of the cast. Most actors are image-conscious and I was on some kind of diet for about 20 years. However, since I took up running I eat what I like and I haven't been near scales for five years.

During tea break we discuss a possible publicity stunt for the play by doing a group streak at the marathon start. Common decency prevents us from pursuing this.

Get my kit ready for Sunday. Friends and family ring with good wishes and I get tingly and emotional.

FRIDAY: Quiet and productive rehearsals this morning, concentrating on relationships: some good stuff comes out. I'm released at lunchtime to do 5's Company, a live chat show. An old chap in the audience dressed in a pearly suit gives me pounds 5 for the Heart Foundation. He ran the London Marathon in 1984, aged 64, and since then has raised pounds 90,000 for cerebral palsy. Fly back to rehearsals and run through what we've done this week. A bit patchy as we're groping for words. I feel end-of-the-week-ish and mind-somewhere-else-ish.

At home Chris frets about doing a gig with his band, Kite, at the 12 Bar Club this Sunday after we've run, so we organise massage. Thirty-six hours to go: rest, eat, worry, but inevitably let it all go - there's nothing left to do now but run.

Cathy Shipton appears in 'Steaming' at the Piccadilly Theatre from 1 May.