[gboss]

Well given that intense heat wave that hit the UK a couple summers ago where the country went from green to brown from space, I’d worry about forest fires

[csvm]

There aren't many forests, and those left aren't big.

[TheOtherHobbes]

There are large parks, and much of London is leafy. The limiting factor is wind. So far it's extremely unusual in the UK to have very dry conditions with strong winds, so fires are much less likely to spread.