Alas, yet another nail in the coffin of great Who actors.
He played many other villains beside's Solon in tBoM, including The War Lord in the Troughton story The War games.
He also appeared in Who on three other occasions.
Firstly in the Krotons as Eelek, then in the T.Baker story The Power of Kroll as Fenner before voicing Victor Schaeffer in the Big Finish audio drama Master.
The man is also well known for appearing in UFO, Space: 1999, and Survivers.
I, however, best remember him as Commander Lutzig in the eternal episode of Dad's Army 'The deadly Attchament'.
Lutzig- I am making note's Cap-a-tain (!). And when we win ze war you will be taken into account.
Mainwaring- You can write all the note's you like your not gonna win this war....
Lutzig- Aw yez wve are!
...........I would go on, but, the rest of this seen has to be seen to be believed.
Utter legend, RIP.