The City of London has no representation in Parliament, unlike HK finance via the functional constituences in LegCo. As for indirect lobbying, I doubt that any business leaders would ask MPs to block the legislation. It's got nothing to do with them - besides, they prefer a bigger labour market, means less upward pressure on wages.
For goodness sake, are you that ignorant of how Parliaments actually work?
We see Big Business directly lobbying politicians on China policy in Germany.
What makes you think the UK is so different?
The City of London Corporation has a permanent representative who sits right next to the Speaker in the House of Commons.
His job is to ensure the City's interests are protected, and to directly lobby MPs.
And are you blind as to why the City of London Corporation might care about China policy?
The expectation is that the Chinese economy and currency will surpass the US Dollar in global influence.
Call it 2-3x larger.
What matters more to the long-term future of the City of London than having access to the Chinese RMB?
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Extend that to other businesses which have ties to China, which is pretty much all of the big ones.
And remember that China is forecast to grow at 1% this year.
In comparison, the average UK forecast is currently negative 7.9%.
And China is roughly 6x larger than the UK in exchange rate terms.
Given that imbalance and the current situation, China is in a position to selectively punish the UK, at little cost to itself.
The Whitehall Bureaucracy and Business will be pointing this out to Boris Johnson and his fellow Cabinet Ministers.