There are actually a ton of reasons to like London. The engineering talent is close to bay level for fintech/security systems engineers while being 60% of the price, it has 186% deductions with cash back instead of carry forward for R&D spending, it has the best AI researchers in the world and profit from patents is only taxed at 10% in the UK.
If we say that half of innovations came from Alphabet/Google, then most of them (transformers, LLMs, tensorflow) came from Google Research and not Deep Mind.