On the sliding scale of tiredness, I've long since passed dog and am nudging dead. My right eyelid has been twitching since Wednesday and I keep finding shoes in the laundry basket. The only thing that has kept me going was the prospect of this holiday, and now we're on a mountain, the Algarve spread out gaudily below our lemon grove. Susannah, who I haven't seen in six months, has arrived from Madrid, and, after two all- nighters and a charter flight, my only thoughts are of sleep.

It's 57 hours since I got up on Friday. I stagger down to the house for a siesta. Flinging wide the veranda doors, I black out. Dream that my sister is running a cab rank-cum-greengrocer's in Turkey and won't give me a car until I've bought a kilo of cukes. Dream that Angel has caught a plane to Portugal as a surprise.

The overhead light switches on and William is by my bed. Though I register his face, I'm convinced it's Angel. "Hello, sweetie," says William, "Angel's on the phone." "Don't be silly," I reply, "You're here." My limbs seem to be pinned to the mattress. William looks confused "Yes, I know. And Angel's on the phone." "I don't understand." He tries another tack. "It's half-past six, darling, and you're in Portugal." I'm still having trouble moving; someone's tied lead weights to all my extremities. "I know," I say crossly. "Oh." We contemplate for a moment. Then "Shall I get him to call back? He's running up an arm and a leg."

"Arr, nooo." I really want to hear his voice. "I'm coming." The straps around the weights come free. I make my way down the corridor, though the walls keep jumping against my shoulders. Pick up the receiver, and Angel says "I just wanted to make sure you arrived okay." "Mmm," I say, "Frango piri-piri con batatas fritas, faish favor". My voice sounds to me like it's coming from the other end of a tunnel. "Serena?" says Angel, "Are you alright?" "Fine." "You sound weird."

I realise what's going on. "Can you wake me up?" I mumble, "I'm sleepwalking." "Urr?" "Wake me up." Angel shouts all the way from London, "Serena! Wake up!" and suddenly I'm shivering in the dark my underwear, clutching the telephone receiver. I put it to my ear. "Hello?" "Hi. Are you awake?" "Sweetheart!" I say, "How are you? What are you doing on the phone?"