Sir Kenneth Branagh has insisted 'Tenet' is a ''different beast'' to 'Dunkirk'.

The 59-year-old actor reunited with director Christopher Nolan for the upcoming spy thriller - having previously with him on the 2017 war epic - but he explained the two movies are very different.

He told Total Film magazine: ''It was a different beast.

''Chris' focus is legendary. In both cases, you're warmly invited, and of course expected, to be on the set from the very beginning of shooting day until the end of the shooting day.

''And to be ready for both what is his very organised and prepared approach, which, as always - and partly, in his case, intentionally - meets the chaos of the day and the imaginations of the collaborators.

''So I would say the level of focus was the same. But in this case, that wasn't provided necessarily by half a dozen massive Second World War ships, but by the complexities and excitement of Christopher's extraordinary idea.''

Although Nolan has kept both the plot and characters in 'Tenet' under wraps, Branagh admitted the filmmaker's approach to getting him in the film was anything but.

He explained: ''It doesn't feel like it's shrouded in secrecy, but, in fact, it is.

''It was as simple as Christopher ringing me up and saying, 'Look, we have this film that we imagine you might not be available for, but if you thought that there was a possibility, the character feels in a sort of fairly compressed way.'

''I'd just about finished Artemis Fowl. We were in prep for Death On The Nile. I talked to my bosses, to make sure that it could work logistically.

''The next evening, Christopher came to see me, and delivered the script by hand, as he had done also with Dunkirk.''

The 'Murder on the Orient Express' star joked: ''It's funny: you get an international master artistic brainiac and a mailman all in one.''