The difference lay in the PCU’s operating methods. Unshackled from the endless backup procedures of the Metropolitan Police, they were able to occupy a unique place in the city’s investigative system. London remained a security nightmare despite its reliance on CCTV cameras, but the Met coped well with mopping blood, drying tears and calming fears; taking care of commonplace crimes was their job. Once, streets like Islington’s notorious Campbell Bunk had existed in gruelling poverty, beyond the boundaries of order and safety. Now, at least, the path was clear for specialist units like the PCU to investigate the misdemeanours that would have gone undiscovered in such areas.

Bryant told every prospective member of staff that their agenda knew no borders of class, age or race. Their remit was to settle sensitive cases with abstruse thinking, their purpose to prevent public panic and moral outrage. In recent years, the unit had become adept at handling the investigations the Met no longer had time to consider in depth. The Home Office now called the shots, and their demand for paperwork had increased until younger, more energetic staff were wasted in the daily untangling of office life that took place behind the crescent windows above the tube station.

As Longbright straightened her seamed nylons and gathered the weekend’s post from the mat, Crippen, the unit’s moth-eaten feline mascot, shot past her into the street, searching for somewhere to micturate. Arthur’s been to the office on a Sunday again and locked the cat in without putting its tray out, she thought. Doesn’t that man ever rest?

She clumped up the bowed stairs in her film-star heels, savouring the emptiness of the unit, wrinkling her nose at the smell of Bryant’s stale pipe tobacco. How long will the calm last this time? she wondered. Peace was both desired and dreaded, for although most of them welcomed a break from the long hours, it turned Bryant into a tyrant, as he stalked about the corridors getting on everyone’s nerves and under everyone’s feet.