Summer 1959. Under the auspices of Pier Paolo Pasolini, HCB, as Cartier Bresson liked to be called, finds himself in Via S. Angelo in Pescheria in Rome's ghetto, trusty Leica in hand. The scene all the more prominent for being in black and white, the cobblestones are lit by a perfect lozenge, a makeshift stage waiting for the protagonist, whoever, to arrive. In the interim, doubling as eerie spectators, two tall-eyed shutters peer down along with some drapes of washing. One, two, three and, as if by magic, into the lozenge spotlight skips a girl. The moment is completed. Click, goes HCB’s Leica: Time stops, not a millisecond too late or early.

Fast-forward to a classroom five decades later. Picture this tired language teacher, his conversation lesson going flat. Having visited the Cartier Bresson exhibition some days before and kept the pamphlet as souvenir, I bring out that very picture. Recognising the district where she lives, one student takes a sudden interest. The lesson revives. I offer her the picture. Fast-forward again, this time a week, and the student’s face is lit with a telling smile. Back at her home in the ghetto quarter, her now arthritic auntie had exclaimed, “But that is me!” adjusting her spectacles at the vision of her eight years young self.

“I’m halfway between tightrope walker and pickpocket,” HCB once described himself, referring to the almost painful anticipation felt before the perfect shot, the ensuing sense of having snatched something quintessential. “To hover quietly, without being seen, then sniff the air and – bzzz – sting!”

Chance and geometry again dramatically come together is in the Behind Gare Saint-Lazare. A shadowy train-spotter is watching what we outside the frame cannot see, when in the foreground, a flat ladder as runway, HCB’s friend Raymond Queneau takes off, his flying figure matched by the sleek trapeze artiste in a ripped circus poster which just happens to stretch off left. Leica alert for this focal moment, then, through HCB’s gap in the fence; snap!: The portly Queneau becomes fellow acrobat, airborne raincoat versus prevailing greyness.

But back to the 1920s, the 12-year-old HCB is himself snapped at a baptism ceremony, camera already in hand as if pointing to the future. In the same room entitled 'Rising signs', two early Cartier-Bresson paintings, as opposed to photographs, show Cezanne as a clear influence. Further on, when HCB paints a nude lolling on a divan, the body’s curves find a sinuous match in the staircase depicted behind.

There follows next a series of trans-European shop-windows where common objects (and body-parts) jumble disquietingly together in a series of surrealist-type still-lifes. With the 1930s came a trip to Africa, confirming HCB’s life-long vocation. HCB had meanwhile imbibed Matila Ghyka’s book Pythagorean rituals and rhythms in the development of western culture. Geometry as archetype, in a photo entitled Asilah, Morocco a stretch of rope has an almost topographical impact; Madrid 1933 transforms a whitewashed wall into a Spartan paradise; windows scan the flat surface like kites. His hat a refulgent black, at the photo’s centre strolls a rotund señor, the unlikeliest of seraphim, no wings needed.

“Instant coalition” is HCB’s term for such an effect. Background geometry once in place, it was then just a matter of the right child, rich man, beggar-man, thief to arrive and complete the scene.

Other surrealist themes appearing in the 1930s pictures would be a series of sprawled figures asleep. Along with surrealism came social commitment. In the The Face of Poverty section, Marseilles ’32 or Mexico ’34 could equally read Lampedusa or Back of Termini 2014.

Also politically engaged but of a different mood are a series celebrating the French Front Populaire’s law introducing a fortnight’s paid holidays for all. Leisure, something of a socialist invention then, is lovingly portrayed. HCB’ slope-eyed views of stout picnickers – together with cheese, baguettes, vin ordinaire – alongside a lazily-flowing Marne or Seine are, for lyricism, up there with Poussin or Claude Lorraine.

HCB also got involved in cinema, the key exhibit here being his 1937 film of the Spanish Civil War. In 1940, as a French army cameraman, he was imprisoned by the Germans. When he escaped in 1943 he joined the resistance. He went on to film the Gestapo building in Paris. In both film and still versions, the exhibition also features The Return, documenting deportees being disinfected against cholera, and more dramatically an ex-Nazi informant at the very moment she is denounced and set upon by a former victim.

More and more, his photography was becoming reportage. Gandhi’s funeral, the 1948 end of the Kuomin-tang, but also an American baseball game are grouped in the section The Century of Crowds. Not that he abandoned the personal portrait. But as HCB puts it, “It’s not easy to put your camera between the skin of a person and his shirt.”

So Matisse sits in his parlour like a cosy magus, totemic doves for company. Giacometti is snapped crossing the street during a sudden downpour. His spindling tilt accentuated by the raincoat pulled up about his ears, the sculptor manages to transform himself into one of his own sculptures.

Again and again, HCB takes the less obvious viewpoint; spectators often prove more fascinating than the event. In an early picture, a French monsieur of unforgettable features and moustache peers through a race-course fence. Or there is HCB, an avowed communist, at George VI’s coronation. In HCB’s depiction the king does not even feature: the scene is stolen by a figure who, having drunk several bottles too many to toast the great occasion, lies blissfully asleep amidst a bed of newsprint.

The show winds to a contemplative close, HCB virtually abandoning photographs for drawing. A photo by his second wife Martine Franck, her own delectable legs from an HCB photo of a decade earlier on display alongside, shows HCB doing just that. Dated 1984-99, self-portraits predominate. Not by chance, his face is particularly alive around the eyes. Swirls of the tensest attention, waiting for that magic moment to arrive. How else? “It’s life that interests me, and therefore the next photo.” Here there are a good 500 by one of modernity’s Old Masters.

Martin Bennett

This article first appeared in the December 2014 edition of Wanted in Rome. The exhbition at the Ara Pacis continues until 25 January.