Kensy leaned against the window and wrinkled her nose. ‘Is this it?’ she asked, as Fitz pulled into the kerb. To say she was underwhelmed was putting it lightly.

‘Sure is,’ Fitz replied, hopping out of the Range Rover. He had arranged for Song to take the car and meet them at the townhouse after their appointment. ‘Come on, we don’t want to keep Magoo waiting.’

‘Magoo?’ Kensy suppressed the urge to say the name again and much, much louder.

‘Don’t worry – I’m sure there’s not a joke in the world your new headmaster hasn’t heard before,’ Fitz said with a grin. He buzzed the gate and spoke into a small intercom. With a noisy click, they were through to the other side.

‘I think this place might actually be a prison,’ Kensy whispered to her brother. The presence of security cameras, and grilles on all the windows, didn’t help to dispel her theory. ‘Maybe Fitz has gone rogue and he’s planning to leave us here.’

‘I don’t think so,’ Max said, pointing to a small sign. It said Central London Free School. ‘Glad it’s free, though, because you definitely wouldn’t want parents paying for their kids to come here.’ The squat double-storey building had all the character of a brown house brick.

Fitz hit another buzzer and was admitted through a steel-framed door into a reception area. A woman wearing thick black-rimmed glasses and a grey cardigan that looked as if it had been made from a Persian cat sat at a desk in the middle of a small glassed-in room. She had short chestnut hair and long manicured fingernails painted a soft mauve. She stood up and walked to the counter.

‘Welcome, welcome,’ she trilled, her face lighting up the otherwise glum space. ‘If you could be so kind as to write your names in here,’ she said, indicating to a ledger, ‘Mr MacGregor will be with you shortly.’

Fitz entered his name first, then the children’s. ‘Thank you,’ he said, glancing at the woman’s badge, ‘Mrs Potts.’

The woman smiled and motioned to a row of beige vinyl chairs on the opposite wall. ‘Please take a seat.’

Kensy could feel a piece of torn fabric poking into her leg and began picking at it until Fitz cleared his throat. ‘I think they need some new furniture,’ the girl remarked quietly.

She and Max looked around the room. There was a poster about bullying and another advertising a bake sale stuck up on the glass that enclosed Mrs Potts’s office. On the far wall above a set of double doors with glass in the top of them was an honour roll dedicated to the school’s head prefects.

One of the doors flew open and a tall lad with wild curly hair thundered through, struggling to balance a huge backpack, a sports bag and a cello case.

‘Aren’t you forgetting something, Alfie?’ Mrs Potts called after him.

The boy, who was halfway out the door, skidded to a halt and hurried back. ‘Sorry, Mrs P. I’ve got a dentist appointment, and if I miss it I’m a dead man.’ He scribbled his name in the ledger, then waved with his free hand and ran out the door.

‘What a giant,’ Max gulped. The boy named Alfie looked like he could have done with a shave. ‘He must be the biggest primary school-kid I’ve ever seen.’

‘Oh no, dear, Alfie’s in Lower Sixth,’ Mrs Potts assured him. ‘Our school caters for students from juniors right through to A levels.’

Max raised his eyebrows at Kensy. This was going to be different.

The headmaster’s door opened and a tall, broad-shouldered man in a smart pinstriped suit walked out. He had a pelt of unruly snow-white hair and a tanned complexion, as if he’d just spent a week on a sunny ski slope. Fitz stood up and the two men greeted one another more heartily than the children expected.

The headmaster shook Fitz’s hand then slapped him on the back. ‘It’s good to see you, old boy.’

‘Magoo, how long has it been? Gosh, you’re looking fit,’ Fitz said. ‘What have you been up to?’

‘Spent the summer in the Azores and acquired a perma-tan,’ the man replied with a grin.

Kensy and Max pulled faces at each other.

The headmaster turned his attention to the children. ‘Now, who do we have here?’

‘This is Max and his twin sister, Kensy,’ Fitz said, nodding at them both.

The children stopped gawping and got to their feet, exchanging small hellos and shaking the man’s hand one after the other.

‘Well, come through and let’s have a chat, then we’ll have you suited and booted, ready to start tomorrow morning,’ the burly man said. He led the way into his surprisingly well-decorated office that, oddly enough, wouldn’t have looked out of place at Alexandria.