All in the above 2 posts are correct.
In RAF service VC10 cruises at M.84 or M.82 dependant on the variant, and a maximum normal operating limit (currently) of M.866 in the cruise in RAF service (mainly due to the fact that we've got things sticking out the front, dangling off the wings and want to be economical with fuel!).
M.94 is the Mne (Vne varying with altitude from 397KIAS@sea level up to 371KIAS at 28500ft).
So what's the Mne of the 990? Sadly the internet gives the normal laymans figures (other than the M.91 cruise - which arguably, if fuel was not a player the VC10 could and would manage), which are fairly meaningless.

Looking on the 990, it seems it was quick, but not if you put a lot of fuel in (in the carrots!).
As an aside, it was interesting that both the VC10 and CV990 used aerodynamic devices invented by Mr Kuchemann. The Convair had his "carrots" and the the VC10 has his wingtips!