But it appears he had underestimated the sheer volume and dedication of his supporters.
They turned out in droves to catch a glimpse of the handsome actor as he stepped out in the British capital to promote romantic drama, Remember Me.
The 23-year-old Londoner was back on his home turf with Lost actress Emilie de Ravin, his co-star in the movie, who looked gorgeous in a lacy black Oscar de la Renta number.
All those who had patiently waited along the red carpet, some of them for hours, were certainly rewarded.
Robert happily spent time posing for photographs and signing autographs before heading inside.
Ever since he first appeared as vampire Edward Cullen on the silver screen in 2008, the star has had to get used to fan hysteria whenever he makes public appearances.
But it certainly has its advantages, as Robert explained: "The idea that Twilight can help little independent films push through Alice in Wonderland and £100 million budgets is nice."
Escorting blonde beauty Emilie to the event, the Hollywood pin-up - busy filming new movie Bel Ami in London for the past few weeks – was without his girlfriend, Kristen Stewart, who did attend the NY debut for Remember Me.
While her man was faced with thousands of screaming girls, she was busy with her own promotional commitments, attending the New York premiere of The Runways.
Having showcased a brand new look last week, the 19-year-old again glammed up in a metallic Emilio Pucci dress to join fellow leading lady Dakota Fanning for the Big Apple screening of the biographical drama, which tells the story of Joan Jett's 1970s all-girl rock band.
Kristen stars as Joan in the film, while 16-year-old Dakota takes on Cherie Currie. Both musicians also turned out to show their support.