"This is where the great walk began," Cooper explains. "He's lurching between high spirits and utter despair, filled with self-loathing, going to endless parties, ‘drowning hangovers like kittens'. His father wants him to get a job but Paddy thinks a career is life imprisonment. He's uninstitutionalisable. All he wants to do is write."

Hightailing it out of this Rake's Progress, Paddy walked from the Hook of Holland through Nazi Germany to Constantinople. It took him over a year from 1933-34, much of it spent "in a coma of happiness" recounted decades later in the spellbinding prose of A Time of Gifts (1977) and Between the Woods and the Water (1986). Our little saunter is less than a mile in more than an hour. Yet what we may lack in schloss-hopping mileage and accumulated time, we make up for in rowdiness and delight. This could be a lesser-known ecclesiastical ritual of the Eastern Church, the Adoration of the Paddy. And we all know it will end, as it should, with wine.

We head towards Berkeley Square on roads slick with rain. "Paddy was my earliest model of a travel writer: brave, curious, cultivated and a marvellously gifted stylist," says Thubron, president of the Royal Society of Literature. "It's strange to be walking commemoratively through a world that's not usually associated with him—not the Greece or Eastern Europe which all his readers know, but the London—still pouring rain—from which he set out 80 years ago." 

Here we are a stone's throw from The Running Horse pub on Davies Street, from where Paddy briefly and rather successfully sold silk stockings as an impecunious teenager. Invited to share his tips with his fellow salesmen one evening, he popped a stocking onto his hand and described its properties as though it were a condom. He was fired on the spot. "That was the last sales job he ever had," says Cooper. One night in the summer of 1940, when the London skyline was thick with smoke and flames, Paddy entered Berkeley Square from Piccadilly. "The blaze of an explosion had revealed two sides of that sentimental quadrangle in a disordered wreckage of wood and stone," he wrote. "Only one thing remained standing. Perched three stories high on a tottering pinnacle of rubble was a white marble privy, glowing shyly in this unaccustomed radiance."

We beetle along to Lansdowne Row, where Cooper describes a literary catastrophe on neighbouring Stratton Street, once home to the Baroness d'Erlanger, a rich and eccentric artist: "I think she had a bit of a crush on him." Everyone did. In 1937 or 1938, Paddy left two trunks here full of papers connected with his trans-Europe tramp—every letter, diary and early draft. The Baroness moved home, put Paddy's trunks into storage at the Harrods Depository, only for Harrods to sell them off years later because Paddy had forgotten to pay the storage charge. He had lost everything. There is a collective writerly wince. "Paddy said the pain used to ache ‘like an old wound in wet weather', but I think it was the best thing that ever happened to him," says Cooper. "It sort of set him free, allowing him to remember with advantage."