i am trying to get hold of dvd

It doesn't seem to have been released on DVD at all, from what I can tell. It is on YouTube though, so at least you can watch it there and even download it and burn to DVD if still necessary.

Hopeless and impossible - I know because I'm trying to do exactly the same thing. Three options:

(1) Contact the broadcaster, Channel Five Television in the UK, and ask if you can pay for an HD download of any kind for private use. This is what I too must do... once I get round to it.  Perhaps if a few of us ask nicely, Channel Five might consider this as an option?

(2) If I recall, you can still watch "Cleopatra" on Amazon Prime. Relatively obscure things are often available via such services; although whether you can download them for keeps (except as a screen-save?) I don't know.  But I like to steer clear of the likes of Amazon P, so that's me stumped.

(3) There used to be a huge profusion of semi-legal or illegal movie sites, but they are being gradually chased out of business and in any case the more highbrow material is usually beyond them - above all, in HD.  What makes this farcical is that what's "illegal" in one nation or continent is perfectly dandy in another. No matter: even if you're happy to try something which is legally dodgy, these sites are generally seething with malware.  You shouldn't even open them unless your PC is armoured like a battle-tank.

A rotten shame that honest people are forbidden legitimate access to outstanding work, of a calibre that deserves archiving and repeated viewing. Yes, I'd gladly make a financial contribution for that privilege.  "Cleopatra: Mother, Mistress, Murderer, Queen" is one of the best documentaries I've watched in a long while.

As things stand, we have the worst of all worlds.  Next question: where can anyone in the world buy an HD version of "The Young Poisoner's Handbook", rather than forking out $60 for a grotty old VHS copy?