I've been researching a label 'Darnell of London' and have drawn a blank. Here are two recent purchases, both with the Darnell of London label. I think they both date 1970's although the blue gown certainly gives off a much 'older' vibe. It has a metal zip down the centre-back but the label is exactly the same as in the black dress. Both have lovely beading detail, but especially the blue gown.
I discovered a designer named Eric Plant who worked under the label Darnell of London. He designed some of the stage clothes for British pop singer, Dusty Springfield in the 60s and 70s (see below). That's about all I know. I can't find any information on Eric so if anyone knows any more or if you have clothes with this same label, I'd really love to know. Please post your photos if possible.
Here are my frocks along with labels.
Here are two of the dresses Eric designed for Dusty Springfield. She wore them in the 1960's and the blue one was worn again in 1970 for a TV performance.