Parasol Mushroom - Macrolepiota procera

The cap in intially almost spherical, but expands into a flat cap with a small central bump, or umbo.  It can be very large.  The cap is pale buff with numerous darker coarse scales. It has a long stipe with a zig-zag snakeskin pattern and a bulbous base. There is a large soft ring which may be moved up and down the stem.  The flesh does not turn red when cut.  The spore print is white or pale cream. 

Other Parasols - the Shaggy Parasol Chlorophyllum rhacodes does not have a snakeskin-patterned stipe. 

Photos taken from side and top down

Grows on the ground in woods and fields.

Late summer and autumn

Fairly common in Britain 

https://www.first-nature.com/fungi/macrolepiota-procera.php