The FV 4005 Stage 2 driving in the arena at Tankfest 26.
An experimental tank destroyer with a 7.2-inch mm gun L4, which was a modified version of the BL 7.2-inch howitzer. It’s not only a huge gun, but also a huge turret. However as a SPG artillery piece, this isn’t too critical, no need to be hull down on a hill ridge. The project started in 1951/52, and developed in July 1955. It used a lightly armoured, fully enclosed and traversable turret on a Centurion hull. The project was abandoned in 1957.
I had seen it before when it was a gate guardian to the museum. Since that visit it was restored to full running order.