BR 80300 Post Office Sorting Van
From SVR Wiki
80300 was the first of 96 Post Office sorting vans built between 1959 and 1977 for use in travelling post offices.[1]
As of March 2015, it is on long term display at The Engine House with the interior accessible to the public.
Links
80300 on www.vintagecarriagestrust.org
"Night Mail" on YouTube, a 1936 documentary showing practices that changed little over the following 40 years.