After he finished his emails, Gillard went off to the forensic pathologist.

Mrs Roy’s body was in the mortuary at East Surrey Hospital in Redhill. Gillard hadn’t arrived in time.

for the post-mortem, but was able to catch Dr David Delahaye while he was clearing up. They greeted each other warmly, having crossed paths many times over the years. The Home Office forensic pathologist was a tall, slightly built man with a domed balding head and metal-framed glasses. He looked like most people’s idea of a rocket scientist. Gillard trusted his judgement implicitly.

‘I’ll send you my full report later,’ Delahaye said. ‘But the bottom line is that Mrs Roy died as a result of a dozen or more hefty blows to the head with a metallic instrument. I understand you have found this murder weapon.’

‘Yes, here are the images,’ he said, sliding out a series of photographic enlargements. ‘It’s an old-fashioned weight, but makes a pretty nasty weapon.’

Delahaye peered closely at the photos. ‘Yes, that would appear to fit the bill. Effectively it is a hammer, and was almost certainly used as one. The cranium was fractured in several places on the left-hand side, which does fit with the idea of the cyclist approaching from behind on the left, and swinging perhaps outwards with the right hand, for the first blow. The lady would almost certainly have fallen after the first blow, and subsequent blows would have to have been administered from either a crouching or kneeling position. But it does seem to fit in with the tyre track evidence, and the impression of the tip of the training shoe, which was within two metres of where the body was found.’

Gillard summarised the DNA analysis from the weapon, and mentioned the discovery of the bicycle. Delahaye nodded, then said: ‘I would love to say that this is a straightforward case. But there may be a little bit of a complexity in this. Let me show you the body.’ He walked to one of the stainless steel drawers, and pulled it open. He then slid the surprisingly small plastic body bag onto a gurney and wheeled it under the halogen lamp at the centre of the examination room.

‘Did you actually see the body?’ he asked Gillard, as he reached upwards to put the extractor fan on maximum.

‘Only cursorily.’

‘Well, the victim was wearing a wig, which came off during the assault. Underneath she had thinning hair, possibly alopecia.’

‘Her family mentioned that.’

‘It’s not that uncommon for a middle-aged woman to have thinning hair. However, I would just like to show you this.’ He unzipped the body bag, and despite the extractor fan, a gust of foetid air hit Gillard’s nostrils. He suppressed his gag reflex as he looked at the damaged head. Mrs Roy’s face was pale considering her ethnicity and was encrusted in black, dried blood. On the right-hand side were marks where Delahaye’s circular saw had cut through her skull so he could extract and weigh her brain. Her hair was sparse and a wispy auburn.