He describes his passion for truthfulness several times during our conversation, and it's clear that he considers it the root of all successful performances. It permeates his approach to casting as well: "It's really about meeting the person... communicating with that person, seeing how they respond, seeing if you get on, and seeing if you're going to be able to capture what you're looking for for a particular thing that you're doing. That's really key for me.
"You do make a thousand assumptions as soon as you see somebody. So to meet them in person and to actually have a conversation, you learn so much about them."
Justin Chadwick's directing career is a meander through the recent cultural heritage of the UK. As well as 'The Other Boleyn Girl' and 'Mandela: Long Walk to Freedom', Chadwick has directed episodes of 'Byker Grove', 'The Bill' 'Spooks' and 'Eastenders'.
The last of these is famously hard work. With an extraordinary number of set-ups to handle each day, there isn't much room for lengthy conversations with actors about moments of truth, so what did he take away from it as a director? "I put an incredible amount of work into the prep so I would know - for example - exactly where all the cameras are going to be all the time. It's great because you're doing seventeen pages [of script] a day and it is a really fast paced turnover."
Chadwick reflects on how that experience was useful when he worked on a recent film for Nokia: "On that job, they wanted a 90", a 60", a 30", a 20" and a 10". And they also want some viral moments.
"If you're used to the level of preparation and attention to detail required for something like Eastenders, you get into a rhythm of working... I like to work with a team that's able to move as quickly as that."
And as far as he's concerned, it's a genuine win-win: "Thanks to my television and film background, I'm able to prepare to get on to the set in a way that makes me ready and able to deliver that clearly and quickly, and in a way that keeps everybody happy."
It really is remarkable how Justin Chadwick gives equal consideration to each of his projects as he speaks about them. Many directors who have gone on to direct features do their best to erase the work that got them there and, if they end up back in the world of advertising will tend to hold their nose as they do so. Not Chadwick. It's beguiling to listen to him talk about the challenge of building a rapport between the two lads in the Nokia ad when one was English, the other Hungarian and neither could speak the other's language, and you can tell Chadwick was in his element as he helped the two boys find the story's truth.
Because of his film and television commitments, Justin Chadwick may not always be available for advertising projects, but it's very clear that if you get him, you really get him.
For more on Justin Chadwick, contact Glynis Murray at Tomboy on 020 7492 1819 or via email using firstname.lastname@example.org.