Yes, I agree - a very nice piccie. But there was more than one type that had 4 Conways and a T-tail. Myself and Mr B flew them both!
And interestingly, the VC10 in your picture (K MK3 / Super VC10) had a tailfin tank which held 5.5 tonnes of fuel. It too was a place to stuff extra fuel rather than a trim tank. Although later in the VC10s life, fuel management was changed to adjust the C of G. But this was to conserve fatigue life rather than to save a bit of trim darg.