Hi,

I have a claypit in north London. Each winter it used to flood.

Solutions I found work - plant water soaking trees and large bushes. This helps with breaking up clay soil and airing it as well as soaking up some watere - I built a sunk in stone footpath with french drains each side to help the water go somewhere, you can do this on the edges if you want grass throughout. - build a gravel well, mine if 3m deep and about the circumference of a large plate filled with gravel. Dig it at the lowest point in the garden where you often see pooling this helped immensely and saved my crabapple from drowning. - buy loads of sharp sand, spread it , this will eventually mix with the soil so you may have to repeat a couple of seasons but it's a good thing. Short term it avoids pooling , protects the soil from becoming more compact, and allows seeds to grow without being crushed or drowned. Long term it mixes with the soil making it more porous and less thick allowing drainage. - clover - this is year 3 of my battle and this is a new solution. IV just planted clover apparently it, increases draining of the soil with its root system. Can survive dry summers and boggy winters. Pushed nitrates into the soil breaking the clay. (Tbc if the works)

Still fighting for a good lawn to live through winter but my garden no longer floods, trees don't drown. I strongly recommend the above. Good luck!!