He is best friends with someone he secretly fancies, and is more than a little concerned that telling her will ruin the friendship and weekly lunches/dinners/night outs that occur.

I just wondered how, in terms of advice to give him, whether a friendship can survive something like that? Because telling her wouldn't lead to a relationship, she has made it clear although she is desperate for a bloke, she isn't that desperate...

That's why i shag all my female friends as soon as possible. Unrequited emotional attachments are for wimps.