David Hansen wrote:

I see that the police have picked on another cyclist in Edinburgh
http://edinburghnews.scotsman.com/topstories/Cyclist-fined-after-three-hours.4747444.jp.

If the report is true then the cyclist had working lights on his
bike, though they may have been dim. Thus he was not committing an
offence and the police had no grounds to ask him for his name and
address. Thus the arrest was illegal, just like the fixed penalty
notice.

If "picked on" means "enforced the law"... yes.

He was under an obligation to give his name and address - if requested -
under road traffic legislation.

Subject to the weird and wonderful separate-but-effectively-the-same-as-here
legal system in Scotland, he didn't give his name and address when lawfully
required to, the police would have been within their rights to arrest him
(which oddly enough, seems to have been their view too). If it were
otherwise, how could cycling law ever be enforced?

But no doubt you will be representing him at his appeal.