Still taking its toll: Queen Elizabeth II Bridge at Dartford Crossing is a quarter of a century old

The bridge was opened by the Queen on October 30, 1991.

Under the Dartford-Thurrock Crossing Act of 1988, toll paying should have stopped when the crossing had been paid for - a date deemed as March 31, 2002.

But charges have been kept on under a separate year-2000 Transport Act, with the funds raised going to the Treasury where they are ring-fenced for transport purposes.

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Highways England has proposed building a multi-billion-pound road tunnel under the Thames east of Gravesend in a bid to reduce pressure on the Dartford Crossing.

The Lower Thames Crossing - which will cost an estimated £4.3 billion to £5.9 billion - would be the first new crossing of the Thames east of London since the QEII Bridge opened.

The plan is being opposed by a number of local MPs who want to see new crossings built at Dartford.

Around 50 million people use the QEII Bridge each year, up by 20 million since it was opened.

Steve Gooding, director of motoring research charity the RAC Foundation, said: "Motorists queuing today, particularly those heading northbound into the original tunnels, will be wondering whether the government's plans for a new crossing further down the Thames Estuary will be enough to tackle this notorious bottleneck, or whether the £145 million they pay each year couldn't usefully fund improvements at the existing site."

Highways England's regional director Simon Jones said: "Twenty-five years ago, the QEII Bridge opened at the Dartford Crossing, providing an indispensable extra link across the Thames estuary, helping up to 50 million vehicles cross each year."