Every time Sallie Stevens answers the phone at the village post office in Chiddingstone, her hand brushes a hollow in the shelf behind the counter, worn as deep as a walnut by the hands of 500 years of shopkeepers before her.

She loves every inch of her eccentric workplace and home in Kent on one of the most absurdly picturesque village streets in the country, from the two iron columns said to have been made from Tudor cannon holding up the shop roof, to the 1.2 metre (4ft) high door to her bedroom – claimed to be a security measure for the unloved tithe men who used the room for tax collection, since the doorway was too low for a man to swing a sword.

Nevertheless, after much heart searching, she has put the lease of what is claimed to be the oldest working shop in the country on the market.

"I've been so happy here, I've loved every minute of it," Stevens said, in a conversation constantly interrupted by customers seeking stamps, tea, carrot cake, potatoes, tickets for the next village hall show or local honey. "It has taken me two years to reach this decision, but this is really a job for a couple. I would just like a few hours off on a Sunday afternoon to walk [her dog] Charlie or visit my family, but that's usually my busiest day. "

The premises include a general stores and a tearoom in the converted stables in the backyard. Since she also does cooked breakfasts for walkers and holds regular pizza nights, she often works from dawn till dark.

The "oldest" claim for any premises is always a red rag to competitors but, in 1593 a tailor, John Moody, was recorded as taking on the lease and installing some of the counters still in daily use. Moody's lease was recording a change of tenancy, so the building was probably a shop far earlier.

The building is at least 140 years older, part of a medieval manor house, Burghesh Court, once owned by Anne Boleyn's father, Sir Thomas Bullen, whose main home was Hever Castle a few miles away. Since then carpenters, tailors, hatters and grocers have used the shop, and it has been a post office for more than a century.

The village, a single row of ravishing half-timbered houses ending in a rosy brick pub at the castle gates, has been used as a setting for many films, including A Room with a View, which was partly filmed in the shop, Elizabeth R and The Wind in the Willows.

The freehold of the shop, like the rest of the row opposite the 13th-century church, is owned by the National Trust, which will vet any new tenant and take a monthly rent.

Stevens first saw the building when she was on an outing with her parents one sunny day. The owner was looking for help in the tearoom, and Stevens loved the place so much that she used to drive regularly from Croydon, where she already had two jobs, to work there on Sundays. Eventually she sold her house to buy the business.

She is determined to stay in the area, if only because her father John, a retired electrical engineer who still lives in Croydon, has become a village institution, organising music nights and starring in the village shows."There is a good living to be had here, but it is jolly hard work," Stevens said. "Then I look at it on a day like today and it's just so beautiful, I wonder if I'm mad even to think of selling."