Xsara HDi - multiplug disconnection - how?

[derekrumble]

If you see my reply to a posting at
http://www.frenchcarforum.co.uk/forum/v ... 641#126641

then you will read that I need to undo a multiplug to clean it. It is the one under the bonnet towards the bulkhead at the rear passenger side. I need to undo this multiplug but I slacken off a locking ring but cannot separate the two halves - is there a particular knack? This has beaten me; I don't want to force anything and risk damage.

Cheers,

Derek