hmmm...
How much of the economy does London control..how important it is in policy making when it comes to India or having control over the parliament of UK
London is very important- it's an extremely wealthy region with GDP per capita among the highest in the world. Over 50% of all currency trades worldwide happen in London and it leads the world in commodities, derivatives trading, fintech etc. The City of London pays around a quarter of the corporation tax take and the city hosts one (UCL) and is at close proximity to two ( Oxford and Cambridge) of the world's top 10 unis. It's a very international city with a majority of its population non white and a significant minority born outside the UK- in fact, London counts as the 4th biggest French city based on the number of French citizens living there! Given the parliament, HQs of armed forces and security services are also located in or around London, it's crucial from a financial and political perspective. It's control over national politics is proportional to its size but since everyone who matters in politics resides there,influence in London will achieve more visibility and media impact.