‘If he came up Woodfield Lane and over the level crossing we will have him on CCTV,’ Claire said. ‘I’ll chase that up with Network Rail.’

‘What about tracing the bike?’ Carl Hoskins asked.

‘It’s not going to be easy, despite some pointers,’ Gillard replied. ‘From the photographs Ms Mockett took we should be able to establish the type of tyre, and possibly even the frame size. But there are millions of bikes out there, and records are much poorer for obvious reasons than they are for cars. Having said that, we’ve been granted a bit of a manpower resource, and I’ve asked for searches under every bridge over every stream or canal in the area, and every bit of waste ground to see if the bike has been dumped. I do want to find that bicycle, because judging by the savagery of the attack it is possible that there are blood spatters on it.’

He turned to RIO Rob Townsend. ‘Is there anything from the victim’s phone so far?’

Townsend, a young and fresh-faced officer, said: ‘We’ve extracted all the metadata, and there’s nothing obviously suspicious. It will take weeks to go through it all, but most recent calls and texts were from family and business associates.’

The plate of sandwiches, already depleted by Hoskins and Hodges, was passed around by Gabby Underwood. Claire Mulholland took one, and then asked. ‘Based on the absence of her purse are we treating this as a mugging? CSI’s initial impression of the body is that there wasn’t a sexual assault.’

‘Bike rage,’ Hoskins said.

‘Got to be random, unless somebody knew that she came here regularly to walk her dog,’ Hodges said.

‘These are good questions but I really don’t want to speculate at this stage,’ Gillard replied. ‘That’s certainly the line we should be taking with the press.’

‘There will be plenty of press interest,’ Claire added. ‘You do know this woman is the same Mrs Roy from the TV advertisements for curry pastes and sauces, don’t you?’

‘Is that her?’ Hodges asked, then mimicked an Indian accident: ‘Orissa Originals, made with the freshest spices, and just the tiniest caress of coconut.’ He finished off with a little sideways head wobble. Claire and Gabby rolled their eyes at each other.

‘She’s been on Celebrity Cook Off as well,’ Gabby added. ‘Last series. Homemade samosas, I think it was.’

‘Okay, so perhaps this is a good time to tell you a little more about who she is,’ Gillard said. ‘Christina, you want to fill us in?’

The brunette went over to the laptop and began her PowerPoint presentation. ‘Mrs Tanvi Roy was the chief executive of Empire of Spice Plc, stock market value £120 million. It employs 800 people at production facilities in Slough, Redhill, and Shadwell in East London. Sales were more than £300 million last year, and it reported a pre-tax profit of £12.5 million.’ She flicked through two or three slides which listed salient financial points ‘In a word, she and her kids are very rich. Number twenty-nine of the Sunday Times UK female rich list, at £47 million.’