This confusion is made more prevalent by Windows, which has consistently claimed the UK is in some variant of "GMT", or even "UTC", during summer, often with a timezone name like "GMT Summer Time" (the UK uses BST in summer). For example, right now, the Windows 10 timezone selector is claiming London is at UTC+00:00, even though it's at UTC+01:00 for summer, and earlier versions of Windows would claim it's in GMT.