This was a privately made design that was proposed to the British military in WW2.
It was first built on a custom chassis, then a second prototype built off the chassis of the Universal Carrier, upon which was an articulating section that would lay flat with it for cross country movement. The driver would be within this section, driving on his stomach. The section could then be raised, allowing a pair of Bren machineguns on the end to fire over cover.
The design was not adopted.
Tank Museum video that includes footage of it driving and adjusting machinegun height.
We got so close to tanks that look like scorpions and we just gave up
What could have been… (From Robot Wars movie, 1993).