This month's average so far for the Bloomsbury Wunderground station is 9.9C, and it's only the 11th. It is quite likely to exceed 10C by the end of the month.Several methods have been used to define the subtropical climate. In the Trewartha climate classification system, a subtropical region should have at least eight months with a mean temperature of 10 °C (50.0 °F) or above.
The averages for March and April, taken from the London Weather Centre (not sure where it is?) are 8.0 and 9.8C, respectively, so that's a very likely scenario, especially if you consider how warm the sea is. Fingers crossed!
If March averages above 10C, April in all likelihood will follow suit, and May - October typically average above 10C. That would be 8 months averaging above 10C, putting us in the posh subtropical club
Even if March takes a 180 degree turn and April disappoints us, there should be areas close to walls etc. that will end up subtropical. I'm sure parts of my garden will be subtropical now that the sycamore next door has been cut down and I have more sun, which equals more daytime heat and improves the averages.
Oh, how good it feels to live in the subtropics