…Brodie was too busy trying to take everything in to answer.
At the end of the drive was a sprawling, red-brick mansion. There was a mixture of designs; some window frames painted white, others black and edged with stone. There were sections of pitched roofs, some turrets and green-topped domes.
In places there were thick black beams criss-crossed along the plaster, but some walls were covered in a creamy pebbledash. There were high chimneys and jagged archways, wooden doors and glazed ones, and in front of the main entrance a gravelled forecourt with a circular lawn.
It looked to Brodie as if no one builder had ever quite taken control. It looked unfinished, as if things here still needed completing. The car slowed to a halt. Brodie stared at the front door of the mansion.
In the story she told herself in her head, it looked like an opening to a new world. She was scared. Unsure again, if she wanted to go inside. Two stone statues stood like guards either side of the door and above their heads hung a single lantern. A candle burned inside, the light of the flame bouncing against something small and shiny.
Brodie bit her lip as the driver of the car unloaded her cases from the boot. She thanked him, checked the time on both her watches and the car pulled slowly back down the drive.

…‘You’ll be in Hut 8,’ Miss Tandari explained, as Brodie began her private tour.
‘Smithies lives off site in the village but you can always find me as I’m based in the mansion. Here’s a map to refer to and I’ll help you get your bearings.’
Starting beside Block B, Brodie could see a series of huts of different sizes and ages. Some were newly painted, but some were rather shabby. On the outside of each one was a number marked on the centre of a thick black name-plate.
‘These huts were the heart of Bletchley,’ Miss Tandari explained. ‘In the war codebreakers were allocated to one particular hut. You worked there all the time. Each hut was responsible for different types of code-breaking.’ Brodie nodded.
‘They’re all different. They’ve all got their own histories. Huts 3, 4, 6 and 8 are the most famous ones,’ she continued. ‘Your grandfather worked in Hut 3. The work which happened there changed the course of the whole war.’
It was a simple scheme. Smithies explained normal lessons would be taught in the morning, in order to cover the home-schooled requirement of the plan, and in the afternoon there’d be sessions on code-cracking.
Most of the lessons would take place in the mansion. Some sessions would be held in the huts. There was only one rule. Whatever happened, don’t engage in conversation with the general public. Most visitors to the museum would see only what they expected to see and as long as the children were in their Pembroke uniform, they’d pass for a group on a school trip.
It was, Smithies explained, the very best form of secrecy. The right-under-their nose sort, which was rarely questioned and it was, he added, what made the process so exciting. Miss Tandari taught them ordinary subjects, and for the most part did a very good job of it.
She tried desperately to make the necessary work on primary factors and function machines seem interesting, and every now and then, when she felt the group was flagging, she bought them mini chocolate bars to boost their sugar levels, something Hunter was particularly grateful for but which Tusia refused in favour of yogurt-covered raisins.
Smithies and Ingham split the sessions on codecracking while doubling as curators at the museum. Brodie couldn’t believe there was so much to learn. They covered hidden messages written in lemon juice and revealed by heat; substitution ciphers and some crazy thing called the pigpen cipher.
They even talked about ‘disinformation’ which could be added to codes to confuse those trying to crack them. Everything confused Brodie to begin with. And everything, it seemed, could be used to hide a secret message just as long as you knew where to look.