Lin-Manuel Miranda used son as inspiration for Mary Poppins Returns character

Lin-Manuel Miranda used his son Sebastian as inspiration for his Mary Poppins Returns character Jack.

The Hamilton creator plays lamplighter Jack alongside Emily Blunt as the new Mary Poppins in the sequel to the 1964 original, which starred Julie Andrews and Dick Van Dyke.

To research Jack, a chipper, upbeat character who "finds the light in any situation", Lin-Manuel had to look no further than his four-year-old son Sebastian, who was two at the time.

"(Jack's) just very in touch with his inner child and inner wonder and I had a two-year-old son that was all the research I needed. Any time I needed inspiration I would watch him playing and there I was," he told reporters at the film's London premiere.

The Moana songwriter signed up for the role as soon as he was approached by director Rob Marshall, famed for movie musicals such as Chicago and Into the Woods, but admitted the part "took every bit of my brain to be able to live up to that incredible 1964 original".

The first sequence he filmed was where Jack, Mary and the three new Banks children enter a world animated in an old-fashioned hand-drawn way, much like the sequence in the original.

"Rob Marshall did something incredible which is he brought back hand-drawn animation for the Walt Disney Company, they haven't done it in years, and I'm so glad he insisted on it because it just feels right," he smiled.

The 38-year-old, who also has 10-month-old son Francisco with wife Vanessa, added that the whole shoot was a "total blast" and he felt lucky to be part of a cast which also includes Meryl Streep, Colin Firth and Ben Whishaw.

"Every day was sort of a surreal dream come true," he gushed.

Mary Poppins Returns hits cinemas from 19 December (18).