My parents used the post-war Bartholomew's 1/2" road maps, and I probably learned most of my map-reading skills* by navigating with them as my father drove. I don't think we have any of them at home these days, but I remember them well, and still see plenty in second-hand bookshops.
They are hopelessly out of date now of course, and of little practical use. But they are very colourful. I always liked the robust way they were mounted on fabric, and I still find them attractive in their own right.
The general style seems to have originated at the end of the 19th century for the maps that Bartholomew's produced of Scotland. There's a chunk of Mull here. By the 1920's they were producing similar maps of England and Wales. There's a chunk of Liverpool here. These were derived from the 1" scale Ordnance Survey Popular Edition. They seem to have been widely used as leisure maps (including cycling) by my parents' generation. I probably became familiar with them in the early 1960's, but I suspect the maps I was using dated from ten years earlier. Bartholomew's continued to produce 1/2" to the mile maps into the 1970's.
Until I went back to look at these again I hadn't realised that from the beginning of the 20th Century they described roads as being "First Class", "Secondary" (good), "Indifferent" (but passable by cyclists) or "Not to be recommended to cyclists". Sometimes with variations:
This wasn't done on the basis of some official classification. The information was provided by members of the Cyclists Touring Club, and their logo appeared on the map. I suppose it's an example of crowd-sourcing.
According to this, there was a formal arrangement between Bartholomew's and the CTC from 1910-1928. Apparently (from here) CTC had a network of map revision officers who tracked changes in the minor road network and correspondence continued until 1975. Though by then CTC felt that the maps didn't take much notice of the feedback their members were supplying.
I see some similarities between the OSM Cycle Map and the Bartholomew style. I don't know whether there are practical reasons for that, though I suspect there are. I hadn't expected to find a parallel in the way that the underlying data was sourced, but it obviously made as much sense in the past to crowd-source local detail as it does now.
The National Library of Scotland provides detailed scans of old Bartholomew maps for England and Wales, and for Scotland in their extensive online collection. And there's more here.
*(and the ability to travel south without turning the map upside down)