alt Hacker NewsStartups like Builder AI use London because a.) they want to raise money from filthy rich Arab investors and b.) those guys are not known for doing much due diligence. They go more by vibes and hype and who's on the existing cap table. Also c.) they are very comfortable with London because it was so much easier back in the day to launder or siphon away funds from their home countries. London is an extremely popular destination for Gulf Arabs.
You'll get a lot of shady startups of that kind in London for this reason.
Not all Arab investors are bad - for example, funds associated with the Emirate of Abu Dhabi (eg. ADIA, Mubadala) has been extremely successful in their investments explicitly because Tahnoon studied engineering in San Diego (and rolled at Gracie's gym) back in the day.
Additonally, for every failed investment like builder.ai a fund like QIA and MS Ventures has had multiple other successful investments.
The perception of "shadiness" in the London VC scene arises simply because a subset of non-American VC simply does not care about value investing and product-led growth.
Additonally, it's not like the UK doesn't have good VCs and Growth Equity investors - for example Index Ventures and Ballie Guiffold both have a solid track record.
Being overly congratulatory and being overly pessimistic about the UK scene does more harm than good.