Wikipedia
Mainstop was a large British supermarket chain, with branches across the whole of England, which rose to prominence in the late 1970s.
Mainstop branches were large general grocery stores, often featuring in-store specialist departments, such as butchers and bakeries.
The corporate logo consisted of four interlaced rectangles, forming an approximation of the "hash" symbol from a computer font set, turned through 45°, or the letter "x" printed twice, so as to overlap. This logo was used in signage and marketing, and on promotional items, including coffee mugs widely distributed through the late 1970s at the opening ceremonies of new branches.
Mainstop was originally part of International Stores, itself a subsidiary of British American Tobacco. In the late 1970s, the largest International Stores were rebranded as 'Big I' and finally as Mainstop. The 22 Mainstop stores ran at a loss during their brief existence, and therefore 8 were returned to the International Stores fold (until Gateway took them over), whilst the remaining 15 were sold to Morrisons, Co-op and Presto in 1983.