(BBC children's series, 1972)

“The actual vehicle that appeared was former Cardiff 357 (SKG357), a 1959 Daimler CSG6 with East Lancs H35/28R body. They had Manchester 'new look' fronts and the PSV Circle reported that they were believed to be the only short versions of this model in the country.” (thanks Roger Holmes). I gleaned these screencaps from a YouTube clip of the opening and closing credits: