Something like 'Multiblue' do you mean, Bernard?

Or C sieboldii 's first flowers. But there are a few other double flowered ones, not sure of the names though as I have never bothered buying them.

Thanks for your help - you never let me down!

I don't feel as though I've helped...did you look at 'Multiblue'?

Spritz, don't feel as though you haven't helped. The mere fact that you have taken the trouble to reply makes me feel really good. It seems as though Owdboggy's suggestion is nearer the mark, but I think that somehow I must try to produce a photo. The plant belongs to my sister who's a bit of a scatterbrain and buys plants, then immediately loses the label. She has a camera which was given to her by a friend who neglected to include the instructions, so her photos sometimes leave something to be desired! She did take a photo of the flower, but hasn't worked out how to include it as an attachment in an e-mail or include it with a question on GoY. Currently her whole computer setup is chaotic (she can't print her photos because she has lost the driver disc) and she seems to have no alternative but to pay a technician to sort it all out for her.
I may be posting more on this question later, but daren't forecast when that might be!

That makes me feel a bit better, Bernard. She's in a bit of a muddle, by the sound of it - a costly one, as that!

Louise1 and I both have photos of Clem. sieboldii on our 'garden' pages - why not take a look and see if that's what you're looking for?

In fact - Louise has that particular Clematis as her avatar at the moment....:-))))

Spritz, the one in your garden pictures looks the nearest to me. I've sent a copy of your picture to my sister to see what she thinks.

That's good. I hope you got the answer for her. Funnily enough, Louise has now changed her avatar! LOL.