"Sir Arnold Robinson" Order of St Michael and St George /GCMG Royal Victorian Order/CVO MA (Oxon) is a fictional character in the 1980s British sitcom Yes Minister and its sequel, Yes, Prime Minister. He was played by John Nettleton (actor)/John Nettleton. He attended Eton College, then Baillie College with Sir Humphrey Appleby and shares the same views on the running of the country, the government and the Civil Service; indeed, his role is often to provide counsel to Sir Humphrey when the latter is encountering difficulties in defeating Jim Hacker. On occasion Sir Arnold obliquely warns Sir Humphrey that any failures in that endeavour could harm Sir Humphrey's own prospects for advancement, mirroring Sir Humphrey's own threats to his younger colleague Bernard Woolley.
In Yes Minister, Sir Arnold holds the position of Cabinet Secretary. In the last episode, "Party Games (Yes Minister)/Party Games", he retires and is succeeded by Humphrey Appleby/Sir Humphrey Appleby, then Permanent Secretary for the Ministry of Administrative Affairs.
In Yes, Prime Minister, while now retired from the British Civil Service/Civil Service, he is often sought for advice by Sir Humphrey and, on one occasion, by Jim Hacker, when he suspects Sir Humphrey of being a spy (of which he is cleared), in One of Us (Yes, Prime Minister)/"One of Us".More Arnold Robinson on Wikipedia.