From the Topper

This is the cover of the 1968 edition of The Topper Book, the annual super-sized hardback edition of the weekly British humour comic. As is frequently the case for comics annuals, it depicts several of the weekly Topper characters together -- the different strips rarely crossed over, and getting to see all the comic's characters in the same scene was very much the Infinity War of its day -- but one of those characters is not like the others.

That's because one of them is Nancy, whose syndicated daily comic strip has appeared in American newspapers since the 30th October, 1938, initially written and drawn by Ernie Bushmiller (with the authorship changing hands a number of times since Bushmiller's death in 1982), and which also appeared in the Topper by way of reprints of those strips from its first issue in 1953 up until the late 1970s.

As far as I can tell, Nancy was one of only two cases of an American newspaper daily being transplanted into a British humour comic in this way, and was presumably chosen because she didn't clash with the other strips in the Topper; Mutt and Jeff ran in the Topper's sister publication the Beezer in 1962, but this does not appear to have been a great success, as it was phased out after about a year. (Nancy started out as a "topper", which in American newspaper comics is a second comic integrated into the larger Sunday strip, but that just seems to be an amusing coincidence.) The cover of the 1968 Topper Book was the only time Nancy was featured in a cover illustration alongside other, original characters from the comic, and looks like it may have been done by a DC Thomson artist directly tracing over some original Bushmiller art; it's interesting to note that she made it onto the cover of the book with the comic's most popular and recognisable characters, ahead of Topper originals such as Nick Kelly.

The Topper annuals featured one or two Nancy Sunday strips, some altered to fit more successfully than others:

Ernie Bushmiller is credited here; crediting writers and artists eventually became standard practice in the Beano by the time it was the last British humour anthology comic still going in 2012, but was pretty much unprecedented before then.

And I can also show you how that last one originally appeared in American newspapers for comparison:

One final thing is that various other illustrations in the annuals, typically on the endpapers, also showed the comic's different characters interacting, including Nancy. And whilst the 1968 Book's cover might have been a case of transplanting Bushmiller's art, for these it looks like it might have been another artist closely copying his style:

So, if anyone ever asks you for all the different illustrators Nancy has had over the years... there may be one whose identity remains unknown. Possibly.