He has appeared in supporting roles in films The Jungle Book (1994), Titanic and television series Game of Thrones, in which he recurred as Ser Rodrik Cassel.

Ronald Porter was born in Dundee, Scotland and educated at Madras College, St Andrews [1] where he performed in three school plays: Serjeant Musgrave's Dance [2] in 1972, A Man For All Seasons [3] in 1973 for which the newspaper review said "Ron Porter was impressive from start to finish, handling a mammoth part with apparent ease, giving a sensitive, subtle and well-controlled performance, especially in the second act", and Taming of the Shrew [4] in 1974 for which the newspaper review said "Ron Porter's affability shines out like the proverbial beacon ... as the most experienced member of the cast, he has the confidence to be able to establish an immediate rapport with the audience.

Following the success of this play members of the cast founded the a cappella vocal group The Flying Pickets in 1982, but Donachie left before their 1983 Christmas number one hit.

— Six Characters in Search of an Author – Mark Fisher, The Guardian [7]When Ron Donachie takes the stage as Deputy Governor Danforth in the second half of Arthur Miller's classic, it's as if this 17th century parable of superstition and intolerance has a new centre of gravity.

But it's also that, in presenting himself as reasonable, considerate and fair, he puts you in mind of every leader who gets his way by masking ruthless force with politeness.— The Crucible review – Mark Fisher, The Guardian [8]Donachie married Fiona Biggar, a complementary therapist,[9] in 1989; the couple have two children: the actor Daniel Portman and Naomi Porter, a linguist.