[sparky_75]

Interesting. Thinking about it, I guess the cake was simply a replacement for the coloured diagonal striped logo used in trails and continuity which also co-existed along with the sphere. Perhaps someone at a later date decided the cake was such a strong logo it was worth making the official logo.

The origins of the 'cake' (how I've always hated that description!) are there in the very first opening moments of Central's first day.

The black and white version of the logo used on trailers shows 14 stripes for the left crescent - whilst the right side is solid. In print (and later on screen) these stripes were shown in 7 colours. 

From there it could be seen how the simplified 6 stripe version came into being (not least perhaps influenced by Channel 4's logo launched late that year!)

www.youtube.com 

A couple of stills from promo showing the colour version:

theident.gallery 
theident.gallery 

Yes - the original design brief included a coloured sphere (as seen on Endcaps, for some continuity links on screen, and on the set of the Presentation studio and Central News)
The B&W striped version - was designed to be used in Print (newspapers etc) and on hot foil press stamped captions. (As many of the captions were back then).
A coloured striped version - which - in the brief was designated to specialised Headed Notepaper only. Though seemed to be adapted for use on screen later on.

The Printed striped version was also used on fabrics (T Shirts/Umbrellas), a white striped one on Pullovers.

I'll have to scan the brief in, as there were a number of alternative looks & styles - some were never used.