Trivia

Like his character Colonel Mustard in the fourth season of Cluedo (1990), Grantham was a convicted murderer. While he was in the army, he shot West German taxi driver Felix Reese in Osnabrück, Lower Saxony on December 3, 1966, in the back of the head while attempting to rob him. He was convicted of murder in 1967 and sentenced to life imprisonment but only served ten years. While at Leyhill Prison in Gloucestershire, he met Louise Jameson who was working as a prison visitor in her spare time. She persuaded him to become an actor.

Trained at the Webber Douglas Academy of Dramatic Arts in London, whose alumni include Terence Stamp, Julia Ormond, Rupert Friend, Angela Lansbury, Matthew Goode, Daniel Hunt, Sue Johnston, Hugh Bonneville and Julian Fellowes.

He loved football and was a West Ham United supporter. He also played cricket for a charity team called "The Bunburys".

In May 2003, he signed a six-month deal to reprise his role as legendary character "Dirty Den", apparently killed and buried in 1989. He signed up to re-appear on screen in September 2003. He returned to BBC's Eastenders BBC1 8:00pm Monday 29th September 2003.

He was ranked #12 in The 100 Greatest EastEnders (1985) Characters of All Time for his performance as Den Watts (2015).

He was ranked #9 in the 100 Greatest EastEnders (1985) Characters of All Time for his performance as Den Watts (2010).

He was bitten by the acting bug as a child but decided to join the army on leaving school,.

Almost exactly a year before he got his big break in EastEnders (1985), he appeared in a small part in Doctor Who (1963) for the same director, Matthew Robinson. Having worked with him in fringe theatre, Robinson suggested him for one of the story's big guest roles as Commander Lytton, the ruthless mercenary helping the Daleks in Resurrection of the Daleks: Part One (1984). The producer, John Nathan-Turner, wanted a bigger name actor, so the more experienced Maurice Colbourne was cast instead. Robinson then offered Grantham the choice of two roles, Galloway or Kiston. Grantham choose Kiston because he had more screen time and was a bigger character in the story overall, appearing in both episodes as the henchman to Davros.

He used to perform a wine slot on a morning programs every now and again.