At Ashridge in the Chilterns, the rules force horses to carry licence discs like cars, and there are plans to introduce a 'driving test' for equestrians. Ashdown Forest in East Sussex now issues licences to horses and their riders for pounds 43.83 a year. No more than 500 are issued each year, and the horses have to carry a small white disc bearing their licence number.
The authority prohibits galloping and cantering during wet periods, when the soil would be churned up, and banned riding altogether for three weeks during the last, sodden, winter.
Similar schemes are being considered for Epping Forest and the New Forest.
Rapidly increasing numbers of horses and riders are, say critics, destroying footpaths, killing trees in ancient forests, eroding precious habitats and littering the landscape with sheds and jumps that often evade planning controls.
The British Horse Society says there are now more horses in Britain - about 750,000 - than at the outbreak of the First World War, when British cities still rang to the sound of hooves and agriculture was driven by horsepower. Today almost all are for recreation.
The society says that about 3.5 million people go riding at least twice a month, and that its membership has doubled over the past 15 years and is still rising. The number of approved riding schools has trebled over the same period.
Successive surveys on the state of the New Forest by the Forestry Commission have shown that more than half its paths have been worn away by horses since the beginning of the riding boom in the late 1960s, while other areas have been churned into bogs. It says it spends tens of thousands of pounds each year trying to repair the damage, but that the ground often takes 10 years or more to recover.
One of its reports says that 'increasing damage to the fabric of the Forest is being caused by recreational horse-riding: precious ground vegetation is scuffed away; incipient erosion on hillside tracks is aggravated by the elements into scars which deface the landscape. As the watchword of the 1970s was the control of the motor car, now it must be the management of horse-riding.'
About 2,000 horses are regularly ridden in Epping Forest, on the outskirts of London. The forest authorities say their sharp hooves and weight damage the feeding roots of trees, often irreparably. The trees frequently keel over.
James Shorten, planning officer for the Council for the Protection of Rural England, says that riders often stray off bridleways on to footpaths reserved for walkers, and that this 'stirs up a lot of heat'. He adds that horses are often 'intimidating and unpleasant both to the legitimate footpath users and to people who have property close to the footpath'.
He also says the character of many landscapes in the Home Counties has been changed by fields full of loose- boxes, field shelters and jumps that often slip through the planning net.
The National Trust allows only 150 riders to use its properties at Hatfield Forest in Essex and the Ashridge estate in the Chilterns.
Epping Forest has its own licensing system awaiting approval by John Gummer, Secretary of State for the Environment, which it plans to introduce next spring. In the New Forest, the Forestry Commission plans to charge riders.
The British Horse Society says it intends to tackle the problem by introducing a new voluntary 'off-road riding test' for equestrians next year.