Nowhere in Britain is power more concentrated than in the countryside. Some people claim we have the second lowest distribution of land in the world, after Brazil.

Because - thanks to the resistance of the landlords - there is no comprehensive record of who owns what, we can't be completely sure. But in 2002 Kevin Cahill's book Who Owns Britain and Ireland estimated that 69% of the land is owned by 0.6% of the population. It has intensified since then: government figures show that between 2005 and 2011 the number of landholdings in England has fallen by 10%, while the average size of holding has risen by 12%.

Possession translates into power. Little can be done in the countryside without the blessing of the tiny minority who own most of the land. They tend to be more resistant to progressive change than the rest of the population, and have successfully delayed or prevented measures that many other people favour. Their power is the reason why it took so long to secure a right to roam in England and Wales, why wildlife is so poorly protected, why we have been slower than any other country in Europe to restore unproductive land and reintroduce missing species, and why atrocious practices like snaring and the continued use of lead shot (rather than non-toxic substitutes) continue.

You'd think that landowners, with their hegemonic grip on the countryside and their tremendous lobbying power - exercised through bodies like the Countryside Alliance, the National Farmers' Union, the Country Land and Business Association and the House of Lords - were powerful enough already. But David Cameron evidently didn't think so. He appointed one of his richest aristocratic chums, the hereditary owner of two vast estates and a good deal of property elsewhere, as minister for the natural environment, water and rural affairs.

The result is that Richard Benyon, the minister in question, is so enmeshed in potential conflicts of interest that were he to recuse himself from all the issues in which he has a personal stake, he would have nothing to do but order the departmental paperclips.

But he does not recuse himself. He repeatedly wields his power in ways that promote his own interests. I have yet to come across a case in which he has acted against them. There has scarcely been a starker clash between public duties and private interests since Ernest Marples, owner of the motorway-building company Marples Ridgway, was made minister of transport, and promptly commissioned Dr Beeching to shut down the railways.

Here are some examples:

1. Benyon was responsible for a policy that, when it came to light, caused the government great embarrassment and forced it into a U-turn. He had sought to use public money to capture buzzards and destroy their nests, in order to help pheasant shoots. By pure coincidence, he happens to own the 20,000-acre Englefield estate in southern England, where he employs gamekeepers to stock it with pheasants and kill the animals that might eat them. Last year I found a video in which one of Benyon's gamekeepers listed buzzards as the first of the predators he blamed for eating his pheasants. Seldom has there been a more self-serving use of taxpayers' money.

2. Across England, birds of prey are still being illegally shot and poisoned by gamekeepers. One of the reasons why the practice continues is that landowners here carry no liability for the killings they commission. When Benyon was challenged in the House of Commons to introduce a law of vicarious liability, making the owners responsible for illegal persecution of wildlife by their staff, he dismissed the proposal out of hand.

3. During Richard Benyon's tenure, Natural England, the statutory body charged with defending the nation's wildlife, has been reduced to a shell. That represents one less headache for the landowners for whom further vast enrichment is a more pressing goal than protecting treasured places. Landowners like Benyon, perhaps, whose Englefield Estate has sold the rights to quarry sand and gravel across 88 hectares of important wildlife habitat, to the great distress of the Hampshire Wildlife Trust.

Now here we go again. This article is about yet another of the minister's potential conflicts of interest.

For many years canoeists, kayakers and wild swimmers have been seeking access to the rivers of England and Wales. In Scotland, as in most parts of the world, the rivers are open to those who can navigate them. But in England and Wales, canoeists and others have formal rights of access to only 3% of our rivers: 1,400 out of 42,700 miles. Everywhere else we are told we are trespassing. We have been denied one of life's great joys: messing about on the river.

There are 2.5 million canoeists and kayakers in this country, and doubtless many more people who would like to jump in the water or take their children for a paddle. But the landlords - primarily those who own or lease the fishing rights - resolutely seek to prevent public use of this great national asset: the waterways that by right surely belong to everyone and no one.

Now here's where it gets interesting. The landowners seem to be asserting a power to exclude that they do not possess. Going back to the 15th century and beyond, there appears to be a general right of navigation on all rivers. As the campaign River Access for All points out, this right was tested in the high court in 2002 (Josie Rowland v Environment Agency, case number HC 0102371.) Mr Justice Lightman ruled that the: "Public Right of Navigation [PRN] may only be extinguished by legislation or exercise of statutory powers or by destruction of the subject matter of PRN eg through silting up of the watercourse."

As no such legislation has been passed, the public right of navigation remains in force. But because landowners and their tenants do not recognise this right, everywhere but on the 3% of rivers where it has been formally conceded, canoeists, kayakers, swimmers and the rest of the public are barred by threatening signs, barbed wire and intimidating men insisting that they are trespassing.

Canoe England, which is also campaigning for access, stresses that it is not asking to navigate every mile of brook and stream. Though canoeing has very little impact on the environment, there are a few places of particular sensitivity where it could be detrimental.

But the general claim the landowners make, that it damages fisheries, is incorrect. A study for the Environment Agency concluded that: "the consensus opinion of the assembled panel of experts is: 'Canoeing is not harmful to coarse or salmonid fish stocks in rivers'."

But the evidence is of little interest to those who refuse to share the rivers: it's not, in reality, about the sensitivities of fish; it's about excluding the great unwashed from their preserves. This is particularly the case on rivers used for very expensive trout fishing, though such sentiments also infect more popular clubs. The Angling Trust lobbies politicians to prevent the recognition of wider rights of access. It is well-placed to do so: its national campaigns co-ordinator is the former MP Martin Salter.

I suspect that on this issue and on others the trust is an embarrassment to some of the anglers it claims to represent. I have met plenty of fisherfolk who have both strong democratic instincts and a great love of wildlife, positions the Angling Trust does not appear to share. I wonder how many would support, for example, the trust's demand that the government should "authorise the trapping and lethal control" of any beavers spreading from Scotland into England. (Beavers were native to these isles until they were hunted to extinction a few centuries ago and have now been reintroduced in two areas in Scotland). I wonder how many would endorse its ecologically illiterate claim that beavers are bad for fish. Studies in both Europe and North America show that their presence in rivers boosts fish populations, as they create shelter and habitat.

As a keen angler and a keen canoeist I have, so to speak, a foot in both boats. I've fished in many of the rivers of Britain, including those frequented by kayakers and canoeists. And I have kayaked on quite a few of them as well.

Paddle down the Wye during the school holidays when - because it is among the very few rivers where canoes are permitted - the river becomes extremely busy, and you'll see a sight which immediately destroys the claim that fishing and canoeing are incompatible: trout rising all around the boats. Where fish are accustomed to them, they quickly lose their fear.

Given that it claims to encourage people to keep fit and to participate in sports, given that there appears to be no legal basis for exclusion, you might have expected the government to clarify the law and either accept the legally established general right of access or change it. But it refuses to do so. Instead it suggests that landowners and canoeists should resolve the issue through "voluntary access agreements".

The problem with voluntary access agreements is that if the landlords don't volunteer, they don't happen. Unsurprisingly they have been a flop: the British Canoe Union has been trying to strike them for nearly 50 years, and has been rebuffed almost everywhere. Without guidance from the government, the issue is resolved in favour of landlords prepared to use force or threats of force to prevent people from exercising their natural and ancient right.

The man currently responsible for the issue is Richard Benyon. During a recent interview with the Angling Trust, he said this: "There will be no change to our policy of supporting voluntary access agreements as the only way forward. Anglers and fishery owners spend a lot of time and money caring for our rivers and streams and their rights deserve to be respected."

But not apparently the rights of canoeists, whose organisations also spend a lot of time and money caring for our rivers and streams.

Benyon has sided with one constituency against another. Now why would he do that? Could it be because he owns fishing rights on the River Kennet and the River Pang?

His estate office tells me that it regards its section of the Pang as closed to kayaks and canoes (in other words "non-navigable"). Benyon leases his fishing on the Kennet to the Reading and District Angling Association (RDAA). Here, his office conceded, "the entire stretch is fully navigable by water craft." This is indisputable: the right of boats to use this water is spelt out in the 1715 Kennet Navigation Act. But has Benyon's Englefield Estate transmitted this fact to the association?

The RDAA's fisheries officer says this on its forum: "Lower Benyons from the weir downstream ... is most defenatly [sic] NON-NAVIGABLE. That means no boats, dingies, rubber rings surf boards etc etc without the landowners permission. All of which I have seen!!" He then goes on name a number of other sections of Benyon's lease which are also "defenatly NON-NAVIGABLE".

Members of the association have proposed their own solutions to the access issue, such as casting at canoes with "a three-ounce zip lead, trebles and 50lb-whiplash braid". "Trebles" means a set of three fishing hooks, welded together at opposing angles.

I would have liked to pursue the question of what advice Benyon's office has given to its tenants, but after confirming that his estate has "interests" on the Kennet and the Pang, and that it regards the Pang as closed, it told me: "We have nothing further to add to our comments."

It is wholly inappropriate that Benyon should be permitted to oversee a highly sensitive issue in which he has an active proprietorial stake. He seems incapable of standing back from his own interests. In fact the nature of his brief makes it impossible for him to do so. If he had any sense of what democracy means, and how it differs from government by the aristocracy, he would spare himself further embarrassment and stand down.

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