As we climb steadily, the sign by the footpath warns of basking adders. To our left, billowing steam from another train rises ethereally between sunlit oaks and beeches. Beyond, another glimpse of sparkling estuary and moored yachts heralds the vistas ahead.

We’re heading for Greenway House, onetime haunt of Sir Walter Raleigh and more recently, holiday home for the queen of detective fiction, Dame Agatha Christie.

Earlier, we began our walk beside the sheltered estuary – one of Britain’s best natural harbours. Moments later, driver and passengers waving, a Kingswear-bound steam locomotive and its rake of cream and chocolate carriages evoked a bygone age.

The smell of the coast, sylvan slopes, bobbing yachts, steam trains and the magnificence of Britannia Royal Naval College across Dartmouth Harbour define the 10-mile Dartmouth Greenway round walk…

In Agatha Christie’s footsteps

In 300-acre National Trust grounds where Christie once plotted Poirot’s adventures, we picnic on a log and gaze back towards Kingswear and Dart-mouth just across the water. By afternoon’s end, we’ll be guzzling Devon ice cream by the town’s beautifully restored Grade 2 Listed bandstand.

But first, our walk only half done, we must take to the water. Ringing Greenway Quay’s famous bell summons a tiny launch that whisks us over to Dittisham – locals say ‘Ditcham’. Today, with picnics packed, we resist the waterside temptations of the Ferry Boat and Red Lion pubs and continue up steep Manor Street. Maybe another time: the reviews and the food on packed tables both look good.

Unfolding estuary views

Paradoxically, continuing another typically South Devonian climb brings us to Lower Dittisham. Higher still, and with more unfolding estuary views, we reach Fire Beacon Hill. Here, a weathered fire basket atop its pole marks the site of a beacon that signalled the Spanish Armada’s sighting in 1588.

Then we descend, contouring down to sleepy Old Mill Creek before making one last ascent to Dartmouth’s hilltop suburb of Townstal. After that, it’s down again through narrow streets and stepped alleys to the bustling waterside and that well-deserved ice cream – or something more substantial in Dartmouth’s former station, one that never saw trains – before catching the ferry back to Kingswear.

Though sun-worshipping adders eluded us, a stunning walk gifted myriad amazing views and rich insight into estuary history. No wonder every Dartmouth estate agent’s window was bloody with ‘Sold’ tags. Whether you’re lucky enough to live here or just exploring for a day, the Dart Estuary’s delights are irresistible.