The Big Business Lark was a radio comedy sitcom of partly satirical form broadcast in 1969. It starred Jimmy Edwards and Frank Thornton and was written by Lawrie Wyman as a spin-off from The Navy Lark, although no characters cross over between the two shows. In a sense, the spin-off element was in the The X Lark name format.
The show was set in the boardroom of fictional company British United Plastics, and was concerned with the business machinations of the chairman, Sir Charles Boniface (Edwards), and his son and deputy chairman, Frank Boniface (Thornton). Plots included landing an order to provide the Red Army with plastic tents, a trip to America to make a good deal from another board member’s mistake and an attempt to find a plastic novelty made by the firm for breakfast cereal boxes.
The main production ingredient of the company is a patented indestructible plastic named Polystumer. It can be moulded for statues (Ep 11), used for novelty items (Ep 10), used as armour for tanks in which capacity it can repel mortar bombs (Ep 12) or used for plastic clothing (Ep 2) carpets, bathroom fixtures and fittings (Ep 1).
The comedy was more broad farce than subtle satire with Edwards playing a bluff, hard-drinking, chauvinist old rogue character and Thornton his more proper sidekick, analogous to the same role he played against Derek Francis in the other Navy Lark spin-off, The Embassy Lark.
Thirteen episodes were made and off-air recordings of all episodes are in circulation. [Wikipedia]
Listen to some episodes at archive.org.