Not the most clearest photo,but the sign on the table reads "AS RIDDEN BY CSM DAY FROM BEACH HEAD TO BERLIN" ,the jug on the table has "DR FUND" wrote on it.

Hodges & Taylor don't identify which RASC unit in 21st Army Group used "541" above an "Army Troops" bar. Apparently based on photographic evidence though, they state "Equipped with Bedford OY Petrol Tankers"