During the short journey, I checked my wallet to make sure I had enough to buy some shoes. £20 in cash and my trusty credit card. No problem. The shuttle stopped inside the airport terminal and I followed the signs for 'Airport Shopping'. They led me to a darkened row of shops in Departures. I began to panic. I asked a passing security guard why they were closed.

"This mall doesn't open 'till nine," he told me. "There are some all-night shops and a duty-free store near the boarding gates ... but you'll need your passport and a ticket to get through."

I panicked some more, then had a brainwave. I ran through the airport, my stocking feet slipping and sliding on the highly polished floors, and found Arrivals. Three sets of double doors were propped open, each with a customs counter. Two were green 'nothing to declare' routes. The third was red. An early morning flight must have just arrived because I could see passengers milling around the carousel waiting for their luggage. The lucky ones were beginning to stream through the two green routes. The attendant on the red counter looked bored and half asleep. I positioned myself at the door nearest him.

"Yoo-hoo, Auntie May, here I am!" I bellowed loudly, waving and gesticulating in the direction of the baggage reclaim. The customs official glanced at me in annoyance.

"No, don't try lifting it Auntie May, it's too heavy. Get someone to help you!"

He looked at me again.

"Remember your hernia, Auntie. You'll hurt yourself," I yelled, shrugging my apologies at the man at the counter. He looked towards the carousel and then at me.

"Can I ...?" I mouthed at him and flapped my hand in the direction of my fictitious relative.

"Yes, yes, go and help your Auntie May," he said, waving me past irritably.

I shot past him and waltzed lightly past the carousels to a staircase at the end of the hall. Taking the stairs like a mountain goat I climbed three floors and found myself on a long corridor lined with offices belonging to various airlines. A quick sprint along the newly mopped corridor brought me to another flight of stairs at the far end. I slapped down the stairs in soaking-wet socks and saw that my plan was a complete success. I was back in Departures but on the other side of passport control. Signs told me Duty-Free Shopping was straight ahead.

Deciding I'd rather have no socks than wet ones I stripped them off and threw them into a waste bin. If I had to buy new shoes I might as well have new socks too. The flooring was ice cold under my bare feet as I tip-toed to the shopping area where, to my delight, I saw a shoe shop that had just opened.

I looked in the window and gulped. The cheapest pair of shoes on display was £99. The male assistant was rather aloof but brought me the cheapest pair of plain black shoes in the shop. A bargain at only £49. They would do fine with a new pair of black socks. I was saved. I gave him my credit card and glanced at my watch ... 7.15 am ... no sweat. Three minutes later he returned.

"I'm sorry sir, your credit card expired yesterday," he teased playfully.

I laughed at the joke, then he held out the card with a straight face.

"What?" I exclaimed, snatching my card. I read the expiry date. It was no joke. Then I remembered that my father had told me there was a stack of letters waiting for me at home. I hadn't bothered changing my address when I'd moved into my Edinburgh bed-sit three months ago. My new card must have been with the rest of my mail.

"Aagh!" I said helplessly.

He had nothing at all for £20 and suggested I try the duty-free minimart.