She had not lost her own habit of vigilance; in the past, it had been imperative; in the past, she had written articles on the subject.

For those of us in constant danger of re-arrest, there is no other option. Are you certain that the fellow coming up the path is the usual postman, or might he be a plain-clothed police officer? That ordinary cove standing eyeing the goods in a shop window – is it possible that he’s eyeing your reflection instead? Be like Janus – look before and behind; be like Argos, possessor of a hundred eyes.

For now, though, there was only the empty path, barred with shadow. Leaving the shelter of the trees, squinting in the sudden sunlight, she crossed the sandy heath towards Hampstead ponds. The fair was immediately louder, the chaos of noise separating as she drew nearer to wild screaming and the yelp of barkers, the crash and clack of flung missiles, the laboured jollity of a steam organ playing pre-war melodies, ‘Daisy, Daisy’ succeeding ‘That Daring Young Man on the Flying Trapeze’. A helter-skelter was visible, and a spinning ride, chairs on long chains whirling around a central spindle, the occupants twisting like marionettes.

Just ahead of her, a rabbit shot across the path. Ten yards behind it, a spherical Jack Russell laboured in pursuit, slowly followed by a gasping Labrador. Their owner was stationary a short distance away, paused in the act of lighting his pipe.

‘Did you receive the canine diet sheet I passed to your housekeeper?’ asked Mattie.

‘And a Happy New Year to you, too, Miss Simpkin,’ said Major Lumb, his voice carrying well in the still air. ‘Fine weather. Shall we avoid snow this year, do you think?’

‘They would live far longer and be much happier were they to lose several pounds.’

‘And I would live far longer and be much happier were my next-door neighbour to stop issuing unasked-for advice. Please pass on my greetings to Miss Lee and wish her a thoroughly sanitary 1928.’ He tipped his hat and turned to follow the pair of animate barrels through the grass.

‘One meal a day and no tidbits,’ called Mattie at his retreating back. The only reply was a puff of yellowish smoke.

She snapped open her handbag and took out a small notebook and pencil, thumbing through to a section entitled ‘COLUMN IDEAS’.

Speaking out, she wrote. Public silence breeds private misery. Dare to be a Daniel.

She was closing the notebook again when the steam organ changed its tune: ‘Daisy, Daisy’ gave way to a jaunty march and the melody looped out of the past and caught her like a snare, so that she stood with the book in her hand, her bag open, her feet nailed to the path.

As I walk along the Bois de Boulogne

With an independent air

You can hear the girls declare

He must be a millionaire.

And instead of the tapering tower of the helter-skelter, she was seeing her younger brother, Angus, his dear, handsome face lop-sided, his indented forehead like a battered tin mug, his lips struggling to supply the words. ‘Just try the nouns this time,’ she’d suggested, rewinding the gramophone, and he’d managed a ghostly vowel for each, while she’d sung the rest with desperate vigour.