Uno Hoo! wrote:
I'm utilising a 'drive drain' at the lower (but widest) end of my new patio
(the drain is the long narrow type - bit like guttering with a metal grille
over). Is it necessary to 'slope' the drain (like with guttering)? The patio
is 9 metres in length at its lower end and because of this long run, any
slope would result in the lowest end of the drain being way below the level
of the flags!

Your entire "patio" should have a slope, the drain follows this
slope. IMO it's far, far nicer to slope the surface to one or
several "low points" which have trapped gulleys and gratings
to underground piping. Accodrains etc. in a domestic environment
are *frightful*.