Page 28 of V2

‘Well I’m sorry to interrupt, but we have work to do. Leave your cases where they are and follow me.’

They returned their teacups to the table. Sitwell led them out of the room, down the stairs, out into the street and across the wide road. They walked in single file. Like a gaggle of grey geese, thought Kay. A few passers-by stopped to watch them. One elderly woman smiled at Kay, and she smiled back.

The bank, like the house, was nineteenth century, with a facade of heavy grey stone. A soldier guarded the entrance. They followed the flight officer inside and stood on the polished wooden floor in front of the tellers’ counter. It was dusty, the air was stale. It felt as if it hadn’t been used for years.

‘Close the door,’ said Flight Officer Sitwell. She waited until it was done. ‘Right, from now on, every time you enter this building you will be required to show your identity card, so make sure you don’t leave it behind.’ She lifted a section of the mahogany counter and pushed open the low door. One of the rear windows had been opened to let in bunches of electrical cables that ran around the skirting board. The mobile radar vans were visible in the distance. The women followed her between the rows of empty desks and down a flight of stairs into the vault. The door to a big safe, lined with deposit boxes, was open. In the dim light, beneath a low ceiling, the sergeants were at work: shifting tables to form a central workspace, setting up Anglepoise lamps, wheeling chairs into place, hanging charts, lifting a blackboard onto an easel, putting out wire baskets, graph paper, slide rules, books of logarithms. Wing Commander Knowsley was seated behind a desk in the corner with three telephones in front of him. Soldiers from the Signals Corps were unrolling cables around his feet.

Flight Officer Sitwell said, ‘Gather round, ladies.’ She waited until they were all in place. ‘So this is where you’ll be working from now on. We’ll be reporting from here direct to 11 Group Filter Room. The GL Mark Threes parked between here and the canal are part of a detachment operated by a new mobile advance reporting unit. 105 MARU will alert us as soon as they detect a V2 has been launched. The watch team, consisting of two officers, will plot the first coordinates of its trajectory, exactly as we practised in England. In addition to radar, there will be backup data from parabolic sound mirrors, but these are to be regarded as a secondary rather than a primary source. If in doubt, use the readings from radar.

‘As soon as Stanmore has the confirmed coordinates of the point of impact, it will be your job to extrapolate the parabolic curve back to the launch point. Each individual officer will work on her own, and then check her findings with her teammate. In case of a discrepancy, the calculations will be checked again, either with me or with Wing Commander Knowsley, until we determine the true result. Team B, consisting of two sergeants, will then convert the data to a map grid reference, which will also be checked before being radioed to Fighter Command.

‘Our objective is to complete the calculations within six minutes of receiving all data. That’s the optimum time to enable our fighters to be over the targets before the enemy has time to fully disassemble their equipment. Every second is precious.

‘Any questions so far?’

Her angular profile swung like a gun turret around the circle of WAAF officers. Louie Robinson raised her hand. ‘When will we be starting, ma’am?’

‘Oh eight hundred tomorrow morning. It will take us until then to get the system up and running. You’ll be divided into four watches of two officers. Each pair will work a six-hour shift. Obviously our aircraft can only attack the launch sites in daylight, so priority will be given to those first two shifts, but don’t despair if I put you on nights: according to the Dutch resistance, the Germans return to the same launch sites and use them again, so what we do overnight will provide targets for attack later.’

Barbara said, ‘Where will we be staying when we’re not here?’

‘I’m afraid there’s no room to sleep in headquarters, although you will be able to spend your rest hours there, and meals will be available. Besides, for security purposes we would prefer it if you were dispersed rather than gathered in a single location. Arrangements have been made for you each to be billeted with a separate family around the town, within walking distance of HQ. I cannot emphasise too strongly that the work you are doing here is most secret. Do not – I repeat, do not – talk about your reasons for being in Mechelen. Remember, the Germans were here for more than four years and only left a couple of months ago. We cannot take the loyalty of the local population for granted. Be wary of strangers, however friendly, and take particular care when you are walking between here and your billeted accommodation.

‘Wing Commander? Would you like to say something?’

Knowsley was talking into one of his telephones. ‘Hello? Hello? Can you hear me?’ He shook the receiver and glared at it. He glanced across at the WAAF officers. ‘Damn thing!’ He slammed the receiver down hard in its cradle and came around from behind his desk.

The maps Kay had seen being loaded at Northolt had now been fixed to big cork noticeboards and attached to the wall beside the safe. One showed London and the south-east corner of England, a second the coast from Ostend to Amsterdam, taking in the territory to the south as far as Brussels; a third showed south-east England and the North Sea as far as the Dutch coast. The fourth – familiar to Kay from Medmenham – was a large-scale chart of Holland from the Hook of Holland to Katwijk aan Zee.

Knowsley picked up a box of coloured pins. ‘Right. This is where we are,’ he said, sticking a red pin into Mechelen, ‘and somewhere around here is where the V2s are coming from.’ He put a pin into The Hague. ‘That’s a distance of roughly seventy miles. As you can see, we’re just seventeen miles south of the port of Antwerp, which is the only city apart from London currently being targeted by the V2. Both are receiving roughly the same number of missiles. For now, we’re concentrating on the London attacks, but our aim in the next week or two is to extend our coverage to include the launch sites that are hitting Antwerp.

‘So, although the street outside looks peaceful enough, never forget we’re on a battlefield, which is why we’re sitting below ground in a bank vault, and why you’re going to be dispersed around the town when you’re not on duty. This is a new kind of warfare – the warfare of the future, I dare say – and we’re attempting something new as part of fighting it. The first rocket will hit London in five minutes. You have six minutes to stop the second. I want you to give it everything you’ve got. A lot of people are depending on us. All right?’ He nodded around vaguely, as if embarrassed at his own theatrics. ‘Good. Carry on.’ He went back to his desk and his silent telephones with evident relief.

Sitwell said, ‘All right, everyone. Find yourself a seat.’

Kay took one of the eight places around the pushed-together tables. Each had been neatly laid with a slide rule, a book of logarithm tables, graph paper, a notepad and two pencils. On the blackboard, the flight officer was making rapid marks in chalk. She stood aside to reveal:

y = ax2 + bx + c

‘We’ll start with the basics.’ She looked down the table. Her eyes rested on Kay. ‘New girl – what is that?’

Kay felt her mouth go dry. She took a guess. ‘It’s the formula for calculating a parabolic curve, ma’am.’

‘Thank God for that,’ said Sitwell. ‘Although you’d have to be pretty dim not to have worked that out, given why we’re here.’ She started writing again, in hard, jabbing motions that sent chalk dust sprinkling to the floor. ‘So let’s see if you can tell me … If the equation is this …’ she gestured to the board:

f(x) = 2x2 + 8x

‘… what are the values of a, b and c?’

Once again she looked directly at Kay. She had a sadistic light in her eyes that reminded Kay of Sister Angela, one of the nuns who had taught her algebra at school and who would hit her on the hand with a ruler if she made an error. For a few long seconds her mind fogged with panic, until years of Sister Angela and days and nights in the Phase Three room at Medmenham came to her rescue.

‘I would say … a equals two … b equals eight … and c equals …’ She hesitated before adding uncertainly, ‘Zero?’

‘Congratulations.’ The flight officer looked slightly disappointed. ‘You have passed your entrance exam.’ She wiped the board clean. ‘Now, ladies, we shall work on some serious trigonometry.’

They worked on through the afternoon. For an hour they practised the basic algebraic calculations required to work out a parabolic curve. Then Flight Officer Sitwell produced a stopwatch and announced they would move on to dummy runs. She chalked up an imaginary set of height and velocity readouts provided by the radar unit, waited five minutes, then gave them the coordinates of the shot-fall of the missile. ‘Go!’ She started the stopwatch.

The sequence of calculations required to plot height and distance, to discover the apex of the curve, to calculate the launch position by converting the distance into miles, and then to locate the origin of the arc on the large-scale map and provide the grid reference – all of it required a level of concentration that made Kay’s head swim. The slide rule became slippery in her sweaty fingers. ‘Six minutes!’ barked the flight lieutenant. ‘You should be done by now!’ And then: ‘Ten minutes! Come on, ladies! Those wretched Germans will be out of the woods and back in their mess drinking beer if you don’t get a move on!’