Just to add a little more detail, it's a Guy Arab LUF chassis fitted with a Willowbrook Viking body and powered by an underslung Gardner Diesel engine. I believe it was built in 1959 and was one of only two Guys fitted with this body, both of them operated by Harper Bros of Heath Hayes, fleet numbers 57 and 58. Both buses still exist in restored condition after falling into disrepair.
Here are a few more pictures: