As she dug beside the base of the bush, attempting to avoid its roots, Mary listened to the noise around her. Neighbours were shouting at their children. Cars from the makeshift garage across the green were tearing up and down the street. The radio was on in the kitchen. Glancing towards the back door she saw a piece of guttering fall from the eaves of the roof. It tumbled through the air and landed next to the garden bench. Mary wondered if it had been meant for her.

Pushing her fair straight hair out of her eyes, Mary directed her attention back to the lilac bush. The roof had waited four years and could last another hour or two. She scooped up the soil and piled it behind her. She dug deeper and deeper until she thought she could pull the roots out without harming them. Lifting the lilac bush carefully, she struggled across the patio and then placed it in a hole she had already dug in preparation.

The spade had fallen down into the pit which, without the bush, was deeper than Mary Rose expected. She jumped down to retrieve the implement and on landing felt something strike the sole of her shoe. Bending over, she pulled a piece of red clay pottery from the ground. It was like the bits of urn on display in the British Museum. Mary wondered if it was Roman. She decided to continue digging.

By the end of the long, warm afternoon she had dug up enough of her garden to make it clear that underneath the ancient roses and herbs lay the remains of a Roman Bath. She uncovered a few square feet of a mosaic-inlaid false floor supported by bricks. Beneath that lay the laudably simple Roman technology necessary for steam bathing. Mary put down the spade and went inside the house for a cup of tea.

In her brightly painted kitchen she sat and thought about the garden. Mary had vague, partially formed ideas about how she wanted it to look. Some plants she liked much more than others; she loathed hydrangeas, for example, but loved sweet peas. She wanted to grow green grapes in a glass house. But none of her plans had at any point included archaeological explorations and the excavation of a Roman Bath. The garden was far too small for such upheaval and, besides, she liked to be alone. A team of archaeologists would get in her way.

‘London is an old town,’ Mary murmured to herself. ‘One is constantly reminded of its age.’ She poured herself another cup of tea. ‘Remnants of the past are everywhere, even in the places where attempts are made to hide them. New buildings somehow manage to age rather rapidly, falling apart after only a few years. It must be the weather,’ she mused. ‘Something about the climate.’

Over a few more cups of tea Mary made some decisions. What would the Archaeologists’ Trust, or whichever public body concerned with this type of remains, think about the fact that she was a squatter? She imagined they would try to buy the building out from under her, or worse still, ignore the fact that she lived there and bulldoze it. Mary would do almost anything to avoid homelessness.

Later, at about midnight and under the light of the full moon, she stood above the hole. Looking down, Mary could see the rudiments of the Roman construction, straight and practical in its design. A cloud passed over the moon as she began to shovel dirt, hoping that the neighbours would not look out of their windows that night.

The next morning Mary slept late. She lay in bed keeping her body still, nursing her tired and sore muscles. Out in the garden was a dark mound that looked rather like a grave.