New allotment

I went to the allotment today I know it's been raining really heavy I'll be in Essex Harlow so I thought I would turn the ground over when I turned one lump over it was like a big puddle in the bottom of it if I did I trench round the edge of the allotment all the water drain off is no water floating on top just underneath I will be much grateful thank you anyone can help

I wouldn't start worrying yet, we've already had nearly all of the rainfall we would expect for the whole month. The water table (the level of water in the soil) will be high right now and you'll only damage it by walking on it/digging it now.

The water does take a while to run through clay - on my old plot on clay, you had to dig in Autumn or wait 'til the soil was drying in Spring.
The RHS says

Warning: if worked or walked on when wet they lose their structure, and become puddled and compacted. Remedying this is slow and laborious; so damage should be avoided at all costs.

Techniques and tips if you garden on clay soil:
•Dig in autumn and early winter when relatively dry. Once wetted by winter rains, clay soils often cannot be worked or walked on until mid-spring
•Allow winter frosts to work on clay and break it down
•Where digging is required, it is traditional in wet regions to dig clay into narrow ridges to allow more frost activity and better drainage
•There is often only a brief period when clay soils are workable between waterlogged soils after winter and baked hard clay from late spring

https://www.rhs.org.uk/advice/profile?pid=620