Thrifty Living: The most startling result of running is the cash saving

Which do you prefer? Pounding the streets at dawn or coming home in the wee hours? Sportsheads or luvvies? Sweat or greasepaint? Until this month I was formerly in the latter camp, naturellement. However, since my stint as theatre critic for the New Statesman was abruptly terminated, I have replaced one with the other. And, what do you know? Forcing myself out on to the windy streets for a run does zero for my appreciation of the West End, but it is a peerless way of saving cash. It gives you a lot of other things too, including endorphin addiction, weight loss and stunning quads, but the cash reduction thing is the most startling.

Let's begin with fitness. We all know it's good to be fit. We also all know it's actually quite expensive to be fit, what with the gym, and the gym café, (which charges £3.99 for an orange juice), and towel hire, and personal trainer hire. So dump the gym and go out on to the streets. All you need is a pair of shoes. Old T-shirts and shorts are fine, and running with an iPod is uncool, as well as unsafe. So you don't even need to invest in any hardware. However, you can still make your daily run excitingly hi-tech, thanks to www.nikeplus.com, a Nike site on which you can work out exactly how many miles, or kilometres, you have run that day. It's a totally addictive pursuit. Just trotting around the roads of your neighbourhood becomes an Official Run, measured by the mighty sports enterprise that is Nike.

Now, because you are fit, you don't find yourself wanting to use cabs. Perversely, cabs come into their own, I find, after you have been sitting down in an office all day. There's nothing like 10 hours on an office chair to make you feel like collapsing into the back of a cab. Whereas going for a five-mile canter around the local park in the morning will conveniently put cab desire back where it belongs. In your dreams. Furthermore, you aren't going out to the theatre, or at least I'm not, so no late nights and cab trips home from the Tube.

Booze is next. Yes, you absolutely have to have a drink when you are at the theatre. Especially if you are sitting through a) a very long Shakespeare involving Ian McKellen in the buff, or b) a musical allied to a TV talent show. But when you are in the midst of a running schedule you find you can replace Merlot with barley water. Also, if you go heavy on the booze the night before, you find you will be running with sandbags on the end of your hips, rather than nice springy legs. So you don't.

Eating out also loses its thrill. Everyone eats out when they are going to the theatre or the movies. I know I have previously advocated eating at home before the show (or even taking snacks for the interval), but frankly it's a tough call. The theatre starts too early, and ends too late to justify eating at home, either end of the night. No, you have to eat out after the show, and thus find yourself dropping £40 on supper. Before you flag down a cab. Whereas when you are nicely tired after your early morning run, you simply feel like eating pasta early with the children.

Thanks to your new, slim frame honed by running, teetotalism, cab denial and a sudden withdrawal of restaurant bread, your old wardrobe has a life of its own because you can suddenly fit into it. Mr Millard is looking very dapper thanks to his alarmingly rapid weight loss, meaning he can now get into things he was too fat for not only on his wedding day, but years before that. All sorts of beloved suits, trousers and shirts have reappeared from the recesses of his cupboard. He also swears that since he has lost 7kg he will be thrashing the soles of his shoes a bit less, but I think this is unlikely.

So, the expensive old West End. When will I see it again? Probably not until 13 April, and even then I won't be swanning about in the foyer of some lovely playhouse in Shaftesbury Avenue. No, I shall be in the vicinity of the Savoy Theatre, but only in terms of stumbling gamely past it en route (hopefully) to the finish line on the Mall. Yes, the grim 26.2 miles of the London Marathon has replaced the bright lights of thespianism for me and I'm hoping that the money I am saving by thrashing around the streets of Islington will be matched by the money I'm thus raising for Help the Hospices.

Sponsor Rosie by logging on to www.justgiving.com/rosiemillard

cash@independent.co.uk