The Place Beyond the Pines' Romina - which hits cinemas in the UK on 12 April - sees Mendes more in baggy jeans and t-shirts than white dresses, the 39-year-old has nevertheless worked a reputation for looking stunning on the red carpet.
So what, according to Mendes, is the secret to staying in the sort of great shape that seems to make strolling down the red carpet a faultless operation? "Well I think you have to be careful what you wear. Know yourself and know what looks good. I do like patterned dresses, but you can get so much out of a plain, uncomplicated dress too by accessorising it in a smart way. Other than that, there is no secret - apart from lemon and hot water every morning!"