This trader advert from December 1951 shows the familiar RP4/RMB portable that looks remarkably like the Vidor CN393.  Roberts were obviously confident enough to leave marketing out of their adverts - no text but the basic description. 

Roberts' Radio

The New RP.4 All-dry.  Price complete with PT 21 Guineas.
The New RMB AC & Battery.  Price complete with PT 25 Guineas.

The New Junior Portable All-dry.  Price complete with Batteries. Waterproof Zipper Cover, including PT £21. 0. 6

Roberts Radio Co. Ltd., Creek Road, East Molesey, Surrey
Telephone: Molesey 2684