Dead Tomorrow

was in the cluttered conference room, which doubled as the canteen and shared communal office, with a mug of coffee beside him, carefully spreading out the photocopy of an Admiralty chart, which Ray Packham had helped him to prepare, on the large table.
    There were charts on the walls, wooden shields, a whiteboard, some framed photos of the team, as well as a bravery award certificate. The view through the window was on to the car park and the featureless grey metal wall of the warehouse beyond. On the windowsill was a goldfish bowl, containing a solitary fish and a toy deep-sea diver.
    Smurf, Jonah, Arf and WAFI were already seated. The young woman sergeant wore a black, zippered fleece, embroidered with the word POLICE and the Sussex Police shield above it. The three men wore blue, short-sleeved shirts, with their numbers on the epaulettes.
    Gonzo, also wearing a fleece, came in and handed Glenn Branson a stiff paper bag. ‘In case you need it.’
    The other four grinned.
    Glenn looked puzzled. ‘Needit for what?’
    ‘To throw up in,’ Gonzo said.
    ‘It’s quite rough outside!’ Jonah said.
    ‘Yeah, and this whole building moves a bit on a windy day,’ said WAFI, ‘so we thought–you know–bearing in mind last time you were with us…’
    Tania Whitlock gave Glenn a sympathetic smile as her team ribbed him.
    ‘Yeah, very witty,’ he retorted.
    ‘Heard you applied for a transfer to this unit, Glenn,’ Arf said. ‘Cos you enjoyed being with us so much last time.’
    ‘ Mutiny on the Bounty springs to mind,’ Glenn said.
    ‘So, Glenn,’ Tania Whitlock said, ‘tell us what you have.’
    The chart showed a section of coastline from Worthing to Seaford. There were three crude red ink rings drawn on it, marked A, B and C , with a sizeable space between each. A green dotted line plotted a course out to sea from the mouth of Shoreham Harbour, with a childlike drawing of a boat at the end of it, beside which someone had written Das Boot . There was also a large blue arc.
    ‘OK,’ Branson said. ‘The skipper of the Scoob-Eee , Jim Towers, had a mobile phone on the O 2 network. These three red circles indicate the O 2 base stations and masts covering this section of coast. The phone company has given us a plot, which is all marked on here, of base station signals received from Towers’s mobile phone on Friday evening, between 8.55 p.m., when it was noticed by a harbour pilot and by a shore boatman passing through the lock, and 10.08 p.m., when the last signal was received.’
    ‘Glenn, are these calls that Jim Towers made?’ Sergeant Whitlock asked.
    ‘No, Tania. When the phone is in standby mode, once every twenty minutes it sends out a signal to a base station, a bit like the way, when I was with you, you radioed the coastguard from time to time and gave him your position, yeah?’ he explained, pleased with his analogy. ‘It’s like checking in–calling home. It’s called, technically, a location update.’
    They all nodded.
    ‘The signal getspicked up by the nearest base station–unless it’s busy, and then it gets passed to the next one. If there’s more than one base station in range, it could be picked up by two or even three.’
    ‘Blimey, Glenn,’ said Arf. ‘We didn’t realize you were a telephone scientist as well as a master mariner.’
    ‘Piss off!’ he retorted with a big grin. Then, continuing, he said, ‘So this is what was happening here. After the boat left Shoreham Harbour, the first location update was picked up by this Shoreham base station and this Worthing one.’ He pointed at the ones marked A and B . ‘Twenty minutes later, the second signal home was also picked up by these two. But the third one, approximately one hour after leaving harbour, was picked up by this third one as well, just east of Brighton Marina.’ He pointed at C . ‘That tells us Towers was steering a south-easterly course–which we’ve marked, as a best guess, with this green dotted line.’
    ‘Good film, Das Boot ,’ Gonzo said.
    ‘Now here’s where it gets interesting,’ said Glenn, ignoring him.
    ‘Oh, great!’ WAFI said. ‘We’ve been waiting for it to get interesting, because it’s been pretty boring so far!’
    The DS waited patiently for them all to stop laughing.
    ‘The timing advance can be anything from zero to sixty-three for a given link with a phone,’ Glenn went on, ignoring their barracking. ‘So if the maximum range is about twenty miles, then divide that