It’s not only the Queen who is celebrating an anniversary this year. Boarstall Tower, the magnificent Grade I-listed gatehouse to the long-demolished Boarstall House, has reached its 700th birthday.

Owned by the National Trust and an important site during the Civil War, Boarstall Tower is rented to Rob Dixon and his wife Pam. Rob started his career as a merchant banker in the City, then switched direction completely, becoming a dealer in 18th-century prints – about which, he freely admits: “I knew nothing at the time”. As we look out over Boarstall’s rolling lawns, I suggest it’s not everyone who would give up a well-paid career to jump into unknown waters.

“I assumed, funnily enough, that I would have a better way of life, whatever that meant. I also assumed that I would earn less money. But in fact I earned more money, to my surprise. Bankers were not paid as much in those days as they are today — if you got one month’s salary as a bonus, you were very excited. It was a totally different culture from today.”

So how did the Dixons end up at Boarstall?

“It was advertised in The Oxford Times. I picked up the paper one day and the property section fell out. On the front there was a colour photograph of Boarstall Tower, available to rent. I thought: ‘Wow, I’ve got to have that’. When I found out the rent the National Trust had in mind, I wasn’t quite so happy. However, we managed to negotiate quite seriously.”

Now Rob Dixon is mounting a four-day festival to celebrate Boarstall’s 700th birthday.

“I just felt the occasion had to be celebrated. The National Trust has been supportive since we got under way, but we had to take on the risk involved. Fortunately, because I’ve loved classical music all my life, and because I’m a director of the Orchestra of St John’s, I know how to hire musicians.”

The OSJ will be presenting an outdoor concert of arias from Mozart operas, and violinist Tamsin Waley-Cohen together with members of the Honeymead Ensemble, will be giving a chamber recital and also a special free concert for autistic children. But the first event will be an illustrated talk by Rob Dixon himself on one of his own specialities, prints made by highly-skilled engravers working from celebrity portraits painted by Sir Joshua Reynolds.

“This was 200 years before Hello! and OK! magazines printed celebrity pictures,” Rob enthusiastically explains. “Eighteenth-century mezzotints after Reynolds were fetching enormous sums by the 1920s: one single proof copy of a print of Lady Waldegrave fetched 2,900 guineas, or £3,045, at auction in 1923. “It’s a huge sum — £120,000 today perhaps? But when the Depression came, the bubble burst. So when I came along a lot later I was able to buy these prints for virtually nothing.”

The festival ends with an outdoor performance of Gilbert and Sullivan’s The Mikado by Charles Court Opera.

“I’m not a great fan of G & S,” Rob confesses. “My grandfather had some pre-electric recordings, which he used to play when I was 11 or 12. They were awful, and put me off. But when I saw this company performing The Mikado, they were just so wonderful that I booked them straight away.”

Boarstall 700 runs from June 21-24. Full details and online booking, visit www.boarstall.com. Phone booking by calling 0845 680 1926.