Offshore? No, Oxfordshire. Those wanting a tax haven need look no further than a toll bridge over the Thames, which is up for sale in David Cameron’s constituency.

Graham Smith, a former wartime RAF pilot, had wanted a little piece of the England he had fought to protect so he purchased the 18th-century bridge 24 years ago — and with it a tax haven.

Next month the bridge will go under an auctioneer’s hammer for at least £1m and give its new owner the perfect defence against Labour’s forthcoming 50% income tax rate. The structure is enshrined in laws from King George III’s reign that mean it enjoys tax-free status.

Motorists cross the stone bridge over the Thames at Eynsham in Oxfordshire almost 4m times a year. Queues of traffic a mile long can build up at peak times, causing pollution and 30-minute delays. It is one of the last toll bridges in Britain still in private hands. Cars are charged 5p each time they cross, and lorries at up to 50p.

The buyer will be exempt from paying any income tax, including the new 50% band, from the £190,000 in tolls collected each year. The bridge will also provide an inheritance-tax shelter and a buffer against stamp duty and capital-gains tax.

A tollkeeper’s cottage comes as part of the sale. Viewing starts this week, and the auction will be held in London on December 3.

“I expect we will see a queue of octogenarians wanting to buy it,” said Neil Mackilligin, senior partner for Allsop, the auctioneer.

“Gordon Brown will hate it. It is a way of passing on your money without it falling into the hands of the taxman. It is a pretty unique opportunity to purchase an investment that produces a good income but does not attract either income or capital tax.”

Smith, a pilot of Lancaster bombers who was an instructor for the famed Dambusters squadron, bought the bridge for £250,000 as an investment in 1985. He died in 2001 but it has continued to give his family a cushion from taxation. It is the last part of his estate to be sold and the proceeds will be divided between his three children.

Michael Hawley, 62, his son-in-law and the bridge’s managing agent, said: “My father-in-law liked unusual assets. This was a piece of old England and he just liked the idea. The family have decided they don’t share the same interests in bridges as he did. It’s as simple as that.”

Hawley, who deliberately avoids the bridge’s queues in his classic Austin Healey sports car, said: “The bridge is already an inheritance-tax shelter but with the advent of the 50% rate of income tax next April, it is clearly going to be attractive from an income situation as well. There is significant interest.”

There is no automated barrier. If the bridge was ever closed, the owner would be forced to run a ferry across. Instead, tollkeepers sit in a booth in the middle of the road and stick out a hand to collect payment between dawn and early evening. There was uproar when the price for cars was increased from 2p to 5p in 1994. A further increase has to be ratified by parliament.

However, not everyone is happy with the bridge. Jane Tomlinson, 46, an artist who uses the bridge to commute to a part-time job with a woman’s charity in Oxford, has started a campaign to scrap the toll.

She said: “It is a testament to the patience of the British public in the way they queue and pay the toll. But it is legalised highway robbery. We should not allow 18th-century transport policy hold us to ransom in the 21st century.”

Tomlinson, who has now switched to a motorcycle to avoid both the queues and the tolls, added: “It is an extraordinary selfish piece of legislation which has nothing to do with providing a service for the local community but everything to do with amassing your own wealth.”

She believes Oxfordshire county council should buy the toll bridge and adopt it as part of the public highway. The county council would not comment.

From pig ford to cash cow

Swinford bridge over the Thames at Eynsham, Oxfordshire, owes its tax-free status to a deal between King George III and the Earl of Abingdon in 1767.

The earl was operating a ferry across the river but agreed to build a stone bridge costing £5,000. In return, the king passed an act of parliament giving the tax-free income from the tolls to him, his “heirs and assigns” for ever.

The bridge was used by farmers to drive their herds of pigs to market in Oxford. Its name is derived from the original “swine ford”.

It has now become a cash cow. Even after the toll attendants have been paid and the bridge painted and repaired, it yields an annual profit of about £100,000.

Under the act, no one can build another bridge within three miles. Motorists from west Oxfordshire have to use it to commute to Oxford otherwise they face a detour on to congested A roads.

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