‘Why on earth was she there?’ Rachel asked. ‘More to the point, how did we not know this before now?’

‘I’ve called the detective who led the crash investigation,’ Ade said. ‘He can’t shed any light on what she was doing there.’

‘I wonder why she’s never mentioned it,’ Rachel said.

‘Maybe she has,’ Ade said. ‘Maybe everyone already knows she was there. Even if she was, it doesn’t matter. It was her husband flying the plane that day, not her.’

Before Rachel could respond, Sam called from the other side of the room.

‘We’ve got something from the ANPR the day Tara was killed. A car registered to Simon Gilbert on the M23, northbound, at 11:05 a.m. The same car is picked up again twenty minutes later on the A23 just south of Lewisham.’

‘What about later in the day?’ Rachel asked, her mind racing ahead as she tried to work out the implications of this new piece of information. ‘He was here being interviewed from about 4:00 p.m. onwards. Which means he’d have to have left London about two hours earlier.’

‘Nothing so far,’ Sam said. ‘But he could have come home a different way. I’ve checked reports for that evening. There was a crash on the M23 southbound, just after Junction 8. If Simon knew about that, he might have decided to take a different route on his way back.’

‘Simon told us he was home all morning,’ Rachel said, standing up and motioning for Ade to follow her. ‘But we’ve only ever had his word for that.’

‘Where does this leave things with Adam?’ Ade said, hurrying after Rachel.

‘I don’t know,’ Rachel said. ‘But before we charge him with anything, I want to speak to Simon and find out why he lied to us.’

She walked along the corridor to the lifts, stabbing the button repeatedly with her finger until a lift arrived.

‘You drive,’ she said, as they left the building and made their way to the row of fleet cars. ‘I need to think.’

In the car, Rachel put out a call for a squad car with two officers to meet her outside the Gilberts’ house at Portslade.

‘What if it was Bella driving the car?’ she asked.

‘Not possible,’ Ade said. ‘She was at work all day, remember?’

‘I’d still like to speak to her.’

The sound of a phone ringing prevented Rachel from saying anything else.

‘It’ll be Sam,’ Ade said, taking the phone from her jacket pocket and passing it to Rachel. ‘He was going to check if there were any other cars registered to Simon and Bella. Can you speak to him?’

‘Only one car registered in Simon Gilbert’s name,’ Sam said, when Rachel answered the phone. ‘2010 Vauxhall Corsa. Same car picked up by the ANPR. Nothing registered in Bella’s name.’