Things have escalated in @Harry Wilson's tackle ’s back garden, but he wanted to assure everyone that it’s boots on the ground and he’s holding his position well …or not 😳
Great job HWT!
https://stagbeetles.ptes.org/about-stag-beetles/
https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/animals/beetles/cockchafer-beetle/
(It looked too big to me on that saw-head and from HWT’s reaction to it but I’m not a very good judge of size from photos so give way to @Coldeanseagull...
Please do not do that - it’s a stag beetle larva as Clamp says - very good for the garden and a priority species for conservation, they are a Red Listed species - it wont do anything to your lawn it feeds on dead wood ffs and will fly away once hatched.
You need to bury it again with rotting...