This region is by far the most heavily subsidised in the UK in reality, which is confirmed by the number of expensive infrastructure projects there such as this one.

London is effectively kept going by these infrastructure projects and so many UK government agencies and businesses being headquartered there. Even the monarchy plays a role, as a massive gravy train mostly based there. All that money keeps other businesses in London going. Every time someone pays UK taxes in any form they are supporting jobs and physical facilities based there. The BBC is another one. People throughout the UK are forced to pay a licence fee that is mostly used to produce content in and about London.

This is part of a repeating pattern. London took massive amounts of resources such as coal, metals and manufactured goods from other parts of the UK which are now in poverty. The North Sea Oil boom of the 1980s, was used to prop up the London stock market, and only a fraction of that money stayed within Scotland which was suffering industrial decline at the time. (Aberdeen has surprisingly little to show for the oil boom and is now a city in heavy decline.)