London in the Spring or the Fall?

For those who have traveled to London or anywhere similar to it in Europe, is it better to go in the spring or the fall? When is the rainy season, tourist season, busy times?

London; the rainy season is all year!!

Autumn is the best because of the residual heat from the summer (if we’ve had one!). Spring can be very cold. We didn’t have a spring last year with two arctic blasts in March and April. And as TS Eliot wrote - ‘April is the cruellest month’.

Bust times? London is always busy. Though the summer is the worst.

I’ve been to London in the middle of spring and it was actually really nice there. Which was rare so I don’t know if it’s the best to start out with cold weather and end with nice. I might have to go with autumn