The popular actor, whose identity as the 12th Time Lord was revealed on Sunday evening, explained that he was shooting on location in Prague when the call came through, and his phone was on silent.
"Ten minutes later, I phoned my agent back," he told the BBC during the live show announcing his new role, "and my agent just said, 'Hello, Doctor.'
"I just started to laugh and I haven't stopped laughing since."
Peter Capaldi has promised that his new Doctor's language will be much cleaner than Malcolm Tucker's
Capaldi is best known, until now, for his award-winning role of Malcolm Tucker in 'The Thick of It'. He reassured family viewers that Malcolm's famously blue tongue would have no place in the Tardis.
"Malcolm has been banished. The new doctor would not put up with any of Malcolm's language or attitudes."
And, in a crowd-pleasing moment, Capaldi accredited the show's long-running popularity to its worldwide fanbase...
"It's an extraordinary show, still here after all this time. The big reason that Dr Who is still with us, is because of every single viewer, at any age, who turned it on in their history.
"Dr Who belongs to all of us."