The Round House was a vast and intricate structure of wrought iron and brick, built to accommodate the turntable used by trains belonging to the London and North Western Railway. Situated in Chalk Farm Road, it was always filled with clamour and action. Since its erection in 1847, it had attracted many visitors but few of them were female and fewer still were as handsome as Madeleine Andrews. In effect, she was a human turntable, making the head of every man there veer round sharply when she entered.

Many engine drivers had taken their young sons to view the interior of the Round House. Caleb Andrews, a short, wiry man whose fringe beard was speckled with grey, was the only one who had taken a daughter armed with a sketch pad. Taller than her father, Madeleine was an alert, intelligent, spirited young woman who had taken over the running of their Camden house when her mother died. Andrews was known at work for his acid tongue and trenchant opinions but his daughter had tamed him at home, coping easily with his shifting moods and taking the edge off his irascibility.

'There you are, Maddy,' he said, raising his voice over the din and making a sweeping gesture. 'What do you think of it?'

She gave a shrug. 'It's magnificent,' she agreed, running her eye over the interior. 'It's like an industrial cathedral. It's even bigger than it looks from outside.'