I had spent most of the day in pursuit of the wit and wisdom of Zara Phillips, as I researched a piece for the sports pages. Job, at least to an extent, done, I was kindly given a lift to Banbury station by the Times equestrian correspondent, Jenny MacArthur.

From there, there is a train that runs furtively, almost secretively, through places called Bicester and Princes Risborough: a back way into London that ends up at the glorious obscurity of Marylebone Station. I found myself, recovering from Zara, staring glassily out of the window, when all at once I saw an angel.

A train tick! A majestic beast of deep russet and deeper forked tail, hanging effortlessly in the air as if flapping were the most frightful bore. And I remembered at once that the train must pass through the Chilterns, for this was, of course, a red kite.

Nor was this an exceptional sighting. They are common, these bloody great birds of prey: they are like sparrows. You must see them every time you take the train. You certainly see them every time you take the M40: I know of birders who invariably park on the hard shoulder for a few minutes to get their fill, feeling that this is safer than twisting and gawping at these glorious creatures at 70mph.

Because you have to look. Outrageous, stunning, impossible: and 20 years ago they weren't even here. Now there are too many too count. Seriously, they are too numerous for an accurate survey. There are a good thousand pairs of nesting red kites in Britain. The first birds were released in Oxfordshire in 1989, they nested three years later and in 15 years of breeding, they have gone from indescribably rare to common-as-you- please.

It is one of the most staggering and visible success stories in the history of conservation. They have been persecuted without mercy; now they are accepted and cherished. It is as much a triumph for humans as it is for kites.

And by God, you need moments like that. Take the most cursory look at the week's disasters. The United States Government is auctioning sites for oil exploration in Alaska that will threaten polar bears, bowhead whales and many species of seabird, including the critically endangered Kittlitz's murrelet.

There are plans to expand the growth of biofuel crops at the expense of savannah and rainforest. The new Defra budget is utterly inadequate for the protection of farmland birds such as skylarks and lapwings, everybody's favourites. The plans for a new tunnel under the Thames march on, despite the certainty that they will destroy irreplaceable marshland.

So good news is to be cherished, to be clung on to; to be celebrated, and not only for its scarcity value. Good things still happen and conservation really does work, and it continues to work. But it doesn't work by saving a bit here and bit there, keeping token little bits of wilderness while destroying anything else you please.

We need a completeness of vision, an understanding that the destruction of the wild matters not for a few birdwatchers but for anybody who does things like eat and drink and breathe. Destroy life and we destroy ourselves. Despair not: you can always raise your eyes to the window and take a quantum of solace in the sight of passing angels.

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