Picture the moment just before you set off from The Stanley Arms in Fishersgate, that scruffy little boundary marker between East and West Sussex where the whole county seems to hinge. The pub sign creaks. Your laces are double knotted. And ahead of you lies 428 kilometres of chalk, shingle, mud and salt air, a full clockwise circuit of Sussex that will take you from the county's inland spine right down to its restless southern edge.

The Sussex Lap stitches together two very different characters into one continuous loop. First comes the Sussex Border Path, threading quietly along the county's boundary with Hampshire, Surrey and Kent. This is the introspective half of the journey, all hedgerows, farm tracks and gentle climbs through 3,460 metres of accumulated vertical gain, the kind of terrain that rewards patience and punishes a runner who goes out too hard.

Then the route turns towards the sea and everything changes. Joining the county section of the King Charles III England Coast Path, you trade inland solitude for some of the most dramatic coastal running in southern England. The chalk ramparts of Seven Sisters Country Park rear up in front of you, each climb offering a view worth the burning legs. Later comes the buzz of Brighton and Hove seafront, pavements full of life after so many miles of solitude, before the route settles into the quieter, tidal rhythms of Chichester harbour as it works its way back towards Fishersgate.

What makes the Sussex Lap so compelling is this contrast built into a single loop. You are never doing the same run twice within it. One stretch has you alone with your thoughts on a border path few tourists ever see. The next has you dodging deckchairs and ice cream queues on one of England's most famous seafronts. Then the coast path pulls you back out to wildness again, birds wheeling over the harbour, the light shifting on the water.

For anyone drawn to the idea of covering an entire county on foot, this is about as complete a way to do it as exists. It demands a broad skill set, the sustained aerobic engine for road and coast path sections, the sure footing for climbs through the Downs, and above all the mental resilience to keep moving through a route long enough to see the seasons change in a single crossing if the weather turns.

The full GPS track and route details are held at sussexlap.co.uk, and the standard route is logged with Fastest Known Time for anyone chasing a record around the loop. Whatever pace you tackle it at, the Sussex Lap offers something rare, a genuine sense of having run the shape of a place, border to coast and back again.