London (CNN) -- There were always three pictures of King George VI on the mantelpiece of the various houses Mark Logue lived in when he was growing up -- including one signed and dated by the king on the day of his coronation -- but as a boy in the 1970s and 1980s, Logue doesn't remember wondering why.
Only years later, after his father died and Logue inherited a box of papers and scrapbooks, did it all begin to make sense.
Logue's grandfather was Lionel Logue, the Australian speech therapist played by Geoffrey Rush in the Oscar nominated movie "The King's Speech."
Mark Logue -- born 12 years after his grandfather died -- had inherited some archive: Christmas cards from the king and queen, a condolence card from George VI to Lionel Logue when his wife died, and a letter of thanks from the queen for a letter Logue wrote when the king himself died several years later.
The papers also include hundreds of letters exchanged by the king and the speech therapist, whom he met more than a decade before he was crowned.
"The content of the letters between them is incredibly friendly as you'd expect between two friends," Mark Logue says. "But there is a kind of etiquette that Lionel still abides by," addressing George VI as "your Royal Highness."
George VI addressed his friend as "Dear Logue," and signed the early letters "Albert" -- his name before he was crowned king. The later letters are signed "George."
Also among his grandfather's papers is what Mark Logue believes is the actual copy of the speech George VI read at the outbreak of war with Germany 1939 -- the climactic scene of the movie.
"In this grave hour, perhaps the most fateful in our history..." the speech begins.
The copy in Logue's archive contains handwritten pencil notes, indicating what words to stress and where to pause.
"The King's Speech" condenses the friendship of the monarch and commoner into about a year, but the real George and Logue knew each other for a quarter of a century.
"The first thing that I came across that startled me was his appointment card," Mark Logue says.
In tiny handwriting, Logue assessed his new patient, Albert, Duke of York in 1926.
The duke "has acute nervous tension which has been brought on by the defect. He is of nervous disposition... Contracts teeth and mouth and mechanically closes throat... an extraordinary habit of clipping small words - an, in , on - and saying the first syllable of one word and the last syllable of another," Logue wrote.
The Duke saw Logue almost every day for next two or three months, in advance of a royal visit to Australia, Logue's records show.
The friendship lasted for the rest of their lives, although it seems they were never photographed together.
At the Coronation in 1937, Logue is seated in the royal box, with his wife, Myrtle. They are so high up, she's using opera glasses.
Myrtle died suddenly of a heart attack after World War II, prompting the king to write: "Dear Logue, I must send you one line to tell you how terribly sorry I was to hear of your bereavement. And I send you all my deepest sympathy in your great grief ...I do so feel for you as I know you had a perfect companionship with her. I am yours sincerely. George."
Mark Logue gets choked up reading the letter generations later.
"It's something about thinking about him hurting after Myrtle's death... makes it kind of real," he says.
The archive inspired him to write a book with the author Peter Conradi.
"King's Speech" director Tom Hooper starting looking at Logue's material about seven weeks before starting filming, Logue says -- and was able to add some details to the movie as a result.
Hooper hadn't known, for example, that the king took off his jacket and stood to deliver the 1939 speech, since photos of the event show him seated and in full military uniform.
And, from Logue's diary, a joke was added.
"I went to Windsor on Sunday for the broadcast... only one mistake... W in weapons," Logue wrote. "After the broadcast I shook hands with the King and congratulated him. And asked him why he stopped on the W. He replied with a grin. I did it on purpose. I exclaimed -- on purpose ? And he said yes -- if I don't make a mistake they won't know it's me."
The movie did make some changes, of course: The real Lionel Logue was more deferential than Geoffrey Rush's character, and rather shorter than his movie counterpart.
And another thing the movie does not tell audiences is that the king and the therapist remained close until the end of their lives. George VI died in 1952. The following year, his friend Lionel Logue died too.