Thanks Companyhotseat.

The trouble is, there are hundreds of indexed links of that form that I want to redirect - so I need a general rerwrite rule so that all requests for ../catalog/blahblah get rewritten as ../blahblah

The following rule is working for me on the test installation on my machine running wamp server, but it won't work on the soon to be live site.

RewriteRule ^subfolder/(.*)$ $1

@Paul - I've tried rearranging the order, but no joy. Why would it work on my Wamp server installation and not on my hosted site - and why are all the other rewrites ok?!?

I'm stumped!