After the WW1 the car sales increased but the War Office cancelled contracts for aircraft engines on the basis they were no longer needed.

In order to keep the design staff busy while other work was found the company took on what appears to be a  project completely out of keeping with established business. A new company was formed, initially named Flickless Projectors Ltd. but was changed to Searchlight Projectors Ltd.

 
The early cinema projectors tended to show a jerky and flickering picture, so efforts were being made to overcome this problem.  G.B.Bowell an inventor had devised a system using an electric motor and a shutter in the shape of a eccentric Maltese cross. Based on his sketches Armstrong Siddeley produced what is believed to be the first motor driven projector. First demonstrated in the Employees Institute; subsequently one was installed in the Alexandra Cinema, Ford Street Coventry.

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John Siddeley's sales efforts caused a batch 200 to be planned. It is known that the well established firm of  Pathe were involved, but it is not known how many were made and sold. By the end of 1923 the company showed a loss and was sold on to a John Olby's  film producing company.

Sadly here the trail ends and no more information  has so far come to light.