Thank you, thank you griffen for stopping me panicking and for being such an allround wonderful guy.
What happened was, it seems, the company asked him to do the usual "little quick fix" at the new offices (they're moving in on Monday, so we'd expected this weekend to be that bit chaotic) on his way "back" from London. I say "back", because Leicester, where the office is, is (I estimate) about 30 miles further north than Coventry :D
He'd left his 'phone in the car because it was going to be a "little quick fix"; alas, there is no such thing as a "little quick fix".
Unfortunately, he's let his carbs run low (he's borderline diabetic) and is getting weak and shaky and sweaty, so I've told him in no uncertain terms to tell his co-worker to get out there and get him some carbs quick. Silly boy, he hasn't eaten since lunchtime, which is asking for it, really. Then, when his blood glucose has got back to being reasonable, he'll be driving home.
*relief* Thank you, Griff.