This is the first in a series of four walks starting from the terminal of one of london’s tube lines. Today, we are starting from the end of the Piccadilly Line: Heathrow, Terminal 5.

There is something deliciously subversive about leaving Heathrow on foot. Everyone else is piling into cars or trains or buses, rushing, rushing, rushing, and you are on foot, using the first and most fundamental means of transport (in case you’re worried, it is legal to leave the airport pedestrian style). But it does not take long to get into the Colne Valley Park and the slow realisation, as planes move like noisy silver fish through the sky, that it was water that formed and still fundamentally affects this landscape.

The Colne Valley Way branches off from the King George VI Reservoir and muddily passes land that is slowly returning to carr, as young alder and willow form dense thickets in the permanently wet ground – watch for the mouldering Land Rover, turned glorious russet by rust.

The River Colne, running in the broad valley down to the Thames, is the chief landscape engineer here and it created its masterwork in Staines Moor, an astonishingly tranquil oasis bounded by the M25, the A30 and any number of air routes. Yet stand among its patchwork of meandering rivers and streams, studded with the metre-high mounds of the Yellow Meadow Ant (some of the nests are centuries old), and you are transported to a time when feet were indeed the only mode of transport, and our ancestors walked the land bridge to Britain.

Wraysbury River also runs through Staines Moor, flowing in blue silence alongside the traffic flowing on the motorway; if you have time, explore, watching for the many bird, plant and animal species that live and visit here.

Leaving the moor, a fairly short walk takes you through Staines itself to the Thames. Walking upstream along the Thames Path, TS Eliot’s description of the river – ‘a strong brown god – sullen, untamed and intractable’ – seems incongruous; this is the river of Kenneth Grahame’s imagining, a river of trailing willows and sentry alders beyond the reach of the treacherous tides of the Thames’s lower reaches, a river where ‘there is nothing – absolutely nothing – half so much worth doing as simply messing about in boats’ and where, when the water breathes mist in the early morning, it really would be little surprise to meet the Piper at the gates of dawn.

Grahame, author of  The Wind in the Willows, lived as a child and again in retirement upstream, and the river, ‘this sleek, sinuous, full-bodied animal’ was his passion. Mole, emerging from his hole and seeing the river for the first time, is entranced, sitting on the bank ‘while the river still chattered on to him, a babbling procession of the best stories in the world, sent from the heart of the earth to be told at last to the insatiable sea’; the walker pacing the miles to Windsor may have little time to sit, but do listen to the river music.

The Edwardian radical John Burns coined the description of the river as ‘liquid history’ (in rejoinder to an American who compared the Thames unfavourably to the Mississippi, Burns said, ‘The St Lawrence is water, the Mississippi is muddy water, but the Thames is liquid history’). Nowhere is this more obvious than at Runnymede, the riverside meadow where King John signed, under pressure, the Great Charter – or Magna Carta – that the king’s will be not arbitrary but bound by law. So ‘no free man shall be taken, imprisoned, outlawed, banished or in anyway destroyed, nor will we proceed against him and prosecute him, except by lawful judgement of his equals and by the law of the land’. Much of England’s later law flows from this charter.

On the hill overlooking Runnymede is the Air Forces Memorial, commemorating and listing the 20,456 air men and women lost during World War II who have no known grave. Also heading uphill, past the John F Kennedy Memorial, the walk passes some of the biggest mansions in the country on Bishopsgate Road before entering Windsor Great Park. The park itself was once a forest, of much greater extent than today, that William I took as hunting grounds for the stronghold he built at Windsor to guard the river. The first written mention of Herne the Hunter associates the horned rider with the forest; in The Merry Wives of Windsor, Shakespeare writes, ‘There is an old tale goes that Herne the hunter, Sometime a keeper here in Windsor forest, Doth all the winter-time, at still midnight, Walk round about an oak, with great ragg’d horns’. Today, the horns more often belong to the deer that inhabit the enclosed deer park. The Long Walk was laid out by Charles II and has been marked out by elm, oak, horse chestnut and London plane trees. As straight as any runway, the Long Walk makes a fitting end to your own long walk from the 21st-century hustle of Heathrow Airport to the medieval calm of Windsor.