Lambert (1st style) derailleur

This original Lambert design may, very well, have been the last derailleur to be manufactured in the UK.

It was also seriously weird! Here are some of its attributes:

It used a version of SunTour's excellent slant-parallelogram design. Which was odd, because, in the early 1970s, SunTour held bomb-proof patents and enthusiastically enforced them. There is a legend that legal pressure from SunTour killed off this design.
It used a Cyclo-style hanger plate of a type used by the Cyclo Gear Company in the late 1950s and early 1960s. I can't think of anyone still using Cyclo ends in the 1970s, so this is a somewhat strange choice.
It was a flat plate design. This was cheap to manufacture, and was a style that was popularised at the time by the Huret Svelto. However it has very short parallelogram pivots that do not respond well to twisting forces. Compared to the Huret Svelto, the Lambert has a long pulley cage and is a slant parallelogram - both of which increase the twisting forces. Huret Sveltos were not famous for lasting a long time - which did not bode well for these Lamberts.
In a world going metric, the Lambert was staunchly imperial - threads, nut and bolt sizes, pulley cage length - you name it.
It used 9 toothed pulley wheels. These had been popular in the early 1960s with the likes of Campagnolo and Shimano - but by 1970 most everyone was using 10 toothed pulley wheels.

My overall take on it is that and its design was probably inspired by a combination of four factors:

Lambert's desire to capture the main features of the best derailleur design in the world (the, then little known, SunTour slat-parallelogram) in an inexpensive package. For example, it has some similarities to a SunTour New Skitter.
I believe that it was manufactured by the Cyclo Gear Company in Birmingham, and displays some of Cyclo's particular obsessions. The hanger plate, pulley cage spring treatment and pressed steel construction are all slightly reminiscent of the Cyclo Benelux Mark 8 Tourist. The main allen key bolts are eerily similar to those of the Cyclo Benelux Sport P2.
The parallelogram plates and the parallelogram spring arrangment are a straight steal from the aforementioned Huret Svelto.
And last, but far from least, there is that 1970s British, price-driven, engineering desperation. It was a time when British manufacturing companies had lost the confidence to 'do things properly' and to then charge the, inevitably high, prices that this entailed. Instead they piled design compromise on design compromise, and manufacutred the resultant mediocre mess on old machines that they could no longer afford to update. It was a recipe for disaster. Who can forget the Austin Allegro?

I think that this is an early example of this basic design. Its features are:

It has no branding at all.
It has pleasantly decent chrome.
It has a cable adjuster.
The cable is clamped using a grub-screw.
There are washers under the shop head (or deformed end) of the parallelogram rivets.