What is this?

What is this?

Observation - What is this? - UK and Ireland. Description: Found in garden under plastic bag on patio. There were around 60+ and they were jumping like fleas. They were very large, around 1cm long. (see pic). Anyone know what it is?

Found in garden under plastic bag on patio. There were around 60+ and they were jumping like fleas. They were very large, around 1cm long. (see pic).
Anyone know what it is?