‘Yes, on occasion during the past year – which were the records I checked, and the dates are marked by Tab N – Mr Starr attended premises in the city of Brighton and Hove.’

‘Are you able to give us, accurately, the address of these premises?’

‘Yes. Number 176A Edward Street, Brighton.’

‘Would I be correct in saying that the premises at 176A Edward Street is in a row of terraced buildings which include a vintage women’s clothing store, a Chinese takeaway and three other law firms?’

‘That is correct.’

‘And is it correct that the ground floor of 176A Edward Street is occupied by a Chinese takeaway called Sun Yip Lee?’

‘Yes, sir.’

‘And is it also correct that the three floors above Sun Yip Lee are occupied by the premises of TG Law, legal aid law practice?’

‘That is correct.’

Cork paused before continuing. ‘A further question: are there any other premises occupying this same address in Edward Street, Brighton, where Sun Yip Lee is located? Somewhere else in the same building that Mr Starr might have visited?’

‘The rest of the building is occupied by the law offices of TG Law. They would be the only other possibility.’

‘Thank you.’ Cork continued. ‘Mr Parker, could you please explain to all of us in this court how the process of identifying the specific location of a mobile phone works in more detail, to help us all understand this better?’

Ray Parker turned back to face the jurors directly and went into expert mode. ‘I need to point out that triangulation between three phone masts gives an indication of the location of a phone but rarely the precise location.’ He drew a large imaginary triangle with his finger as a diagram for the jurors. ‘The phone will be somewhere in the centre of this triangle.’

‘So, you could not be certain which address, precisely, the defendant visited the morning of November 21st?’ Cork asked.

‘Well, yes, I can be, and I will explain how. It is hard to pinpoint an exact location in a rural environment, where several square miles could be covered by triangulating mobile phone masts. But in an urban situation we can be a lot more precise, partly due to the density of masts and partly due to other aids available to us, such as Wi-Fi and CCTV. In this case in particular we can be accurate to within two hundred square yards. That is still quite a big area, including Brighton and Hove Magistrates’ Court and Brighton Crown Court, the premises of Sun Yip Lee, a ladies’ vintage clothing shop, Dig For Victory, the law offices of TG Law, and also the premises of Latest Television and the Argus newspaper, as well as a substantial number of residential addresses. However, we have other tools available to us, as I mentioned, to pinpoint the location more precisely.’