Smith, showrunner Steven Moffat and companion actress Jenna Coleman attended several panels last month as part of the official Doctor Who Celebration at London's ExCel - each packed to the rafters with fans - and the Week in Geek attended the final gathering on Sunday, November 24.
In closing the panel, Moffat paid a lengthy and heartfelt tribute to his leading man and friend, which is reproduced in full below:
"There's the fiction of it and the changeover of Doctors, which is moving at a fictional level, but I'm losing a really good friend. It's a very real and human thing. I'm sitting here knowing that this is the very last time that I'll ever be on a Doctor Who panel with Matt - and we have done so many.
"We've had so many adventures… from the terrifying beginning when Matt had to go outside and say, 'Does anybody want me to sign anything?' and nobody knew who he was. In that first year, I had 'Not Russell' carved in my forehead and Matt had 'Not David' carved in his and everyone just thought we were idiots.
"We just plodded around trying to make Doctor Who and people were saying, 'You're so not making Doctor Who!' - up to the moment where it hit and it became a huge thing. It is Matt's Doctor that has taken Doctor Who to the rest of the world - that is this man's achievement. Let's be clear about that.
"There are occasionally - among sillier Doctor Who fans - attempts to say that [the show] is doing less well than it used to. Doctor Who has never ever come as close to doing as well as it is right now. So much of that is down to Matt. So much of it is the international appeal of this man - he is the Doctor.
"Honestly, you can ask as many people as you like, dig as deep as you like - you will never ever find a negative story about Matt Smith. You simply will not. Everybody adores him.
"He makes the crew work faster. Marcus Wilson [the producer] would always get him to the set quicker than he needed to, just 'cos Matt's presence gets everybody energised. He is tireless - not just in his performances, but with the extra demands of being a leading man, of being the company leader. He is so good at that and yet he works so hard at his own performance.
"I will miss my friend [and] I will miss the most tireless and inventive actor I have ever worked with."
Afterwards, a clearly emotional Smith paid a tribute of his own to Moffat, to his co-star and to the Doctor Who fandom.
"I've been lucky," he explained. "Steven's my greatest friend in this industry as a result of having had four years with him and not only that... the brilliant mind that is The Moff... the imagination... think of the monsters he's brought us, the characters... just the constant invention that is wild and unabashed and breaking new ground the whole time.
"I'm really sad, because you leave your best friends to go and do something else with people who aren't your best friends, which is annoying! You're like, 'You're not Jenna and Steven, ya weirdos!'
"But thanks Moff and Jenna and everyone who's worked with me... and thanks to all [the fans] - it's been the best time. Thank you for having me."
Doctor Who: Matt Smith, Thank you for being the Doctor