Decided on a whim to hunt down Andrew, the opera casting agent I met in Glasgow.
The details I had to hand were sketchy - his surname (which can be spelt two ways), and the memory that he lives in a flat near Chelsea.
A little bit of work with online directory enquiries revealed a small pile of SW Postcoded Andrews that might fit the description, but a rifle through Streetmap placed them all in places like Norwood and Woolwich.
I then checked company directors, and discovered one with a WC1 postcode - which may be possible. But he's a civil engineer.
One option is to ring up an Opera Company and ask if they've heard of him, but I can't think of a way to do it without sounding mad, or like I'm desperate to be in an opera.
Note to self: Next time, easier just to take their phone number.