As part of our data building work for the Global 5000, we keep track of the country where companies are headquartered. With that data we can look at companies by location and by industry. Here’s the list of the largest (by revenue) companies in the UK
Royal Bank of Scotland
HBOS (recently acquired)
Rio Tinto Group
and an honorable mention to Prudential plc who would normally be on the list but whose revenues got wiped out in the financial firestorm over the past year.