I know it’s an old thread, but if anyone is still interested, I think that this vehicle was a prototype made by Glover Webb just before they were closed down.
It was based on the existing Tactica vehicle, but I believe that this one was produced with Rockwell independent suspension rather than the leaf spring arrangement fitted to the standard product.
A quick look underneath should establish that.
Alvis did offer this vehicle, but I’m not sure if the independent suspension was ever introduced into production vehicles. I don't know if BAE have continued the range