as he watched Henderson scribble numbers on to a pad of squared paper.
‘Simple key phrase,’ Henderson explained. ‘It’s relatively easy to decode so it’s only suitable for transmissions of up to about fifty words. For instance, suppose my key phrase is , and I want to send the name Mary had a little lamb Charles Henderson. M for Mary is the thirteenth letter of the alphabet and C for Charles is the third. Three and thirteen is sixteen so I send the sixteenth letter of the alphabet in Morse code.’
‘P,’ Paul said. ‘What if it adds up to more than twenty-six?’
‘You subtract twenty-six from the total. So for example, the fourth letter of my name is R and the fourth letter of my key phrase is Y. R is the eighteenth letter of the alphabet, Y is the twenty-fifth. So I add eighteen and twenty-five, then minus twenty-six equals seventeen. So I send the letter Q.’
‘So you have to do that for every single letter?’
‘Every one.’ Henderson nodded. ‘And the message that comes back from headquarters will be encoded using a different key phrase.’
‘So we won’t get a response straight away?’
Henderson shook his head. ‘There’ll be an immediate acknowledgement if they receive our signal. I’ve got another transmission window on another frequency that’ll be open between midnight and three a.m. for them to send a reply. If we don’t get a reply tonight, I’ll listen out again tomorrow.’
The pink house had steep hills rising up behind and Henderson reckoned they needed higher ground for their transmission to reach London.
Maxine found a blanket upstairs and made a flask of coffee. Paul had been through a long and stressful day, but he’d worked hard on repairing the transmitter and was keen to come along and see whether it worked. Henderson also suspected that Paul might be useful if they had trouble getting a good signal out of the transmitter.
It was a heavy device, intended to send secure transmissions from within the consulate rather than being dragged around hillsides by spies. The Germans had imposed a nine p.m. curfew on the entire occupied zone. This ruled out using the truck, or even walking on the dirt roads that led to the farms uphill.
The pair had to stay off-road. They cut through a hedge at the bottom of the garden, crossed the stream and began to ascend the hillside, which was planted with long rows of vines. At this time of year they bulged with unripened bunches of grapes.
While Henderson strained with the weight of the radio, Paul carried the Morse key, a lead acid battery, a blanket, flask and some bread and p‰té. It hadn’t rained in more than two weeks and the evening breeze whipped dust off the dry ground.
After a quarter-hour they were near the hilltop. At this height it was too windswept for cultivating vines and the uneven grassland was grazed by sheep, who took no notice as the pair found shelter behind a moss-covered boulder.
Paul glanced down the slope, seeing a moody orange sunset illuminating the pink house at the base of the hill. But there wasn’t time to admire the landscape. They’d already hit the fifteen-minute transmission window and even if some part hadn’t worked loose on the trek uphill it would take several minutes to rig up the battery and wait for the valves inside the transmitter to warm up.
Much to their relief the orange bulbs illuminating the signal gauges lit up when Henderson plugged in the Morse key.
‘Nice,’ Paul said, as Henderson manically tapped his coat pocket.
‘Dammit,’ Henderson growled. ‘I’ve left the coded message and my pad on the dining-room table.’
Paul’s mouth dropped open. ‘Are you sure?’ he gasped, knowing they’d never get down to the house and back up the hill before the end of the transmission window.
‘Gotcha!’ Henderson smiled as he pulled the notepad out of his trousers and wafted it under Paul’s nose.
‘Git,’ Paul complained. ‘You totally had me there.’
‘I’m no radio operator,’ Henderson said, as his hand hovered over the Bakelite knob of his Morse key. ‘Read me the letters, slowly.’
‘You should have got Rosie up here,’ Paul said. ‘She learned Morse code at Girl Guides, back in Paris. She got the highest mark in her whole troop.’
‘you tell me,’ Henderson said, as he pulled on a set of headphones. ‘Well, here goes nothing.’Now
‘Q,’ Paul said. ‘T, M, L …’
He carried on reading the letters as Henderson stared intently at his Morse key, tapping out dots and dashes.
When decoded Henderson’s message would