"Sherlock" actor Benedict Cumberbatch attended the Royal Marsden Dinner at Windsor Castle Tuesday where he dared to outshine Prince William in the fashion department! While he's not partying, he takes time to persuade his mom into helping him launch the Chelsea Flower Show on May 19.

The Empire magazine's "Sexiest Movie Star" impressed in a classic tuxedo designed by Ralph Lauren that fit his lean body perfectly. The Duke of Cambridge, meanwhile, was no slouch himself in a black and white suit with a black bowtie.

"So, who do we think looked the best? It's a close call but we're going to have to go with the "Star Trek Into Darkness" actor, whose crisp suit looked as if it were made for his body," the HuffingtonPost said.

The dinner was actually sponsored by Ralph Lauren, according to MailOnline, in order to raise more awareness about the Royal Mardsen Hospital (Prince William is the president of the organization) as well as thank those who contributed to its continued operations.

Aside from "Sherlock" actor Benedict Cumberbatch, other celebrities in attendance were Emma Watson of the "Harry Potter"series; Cate Blanchett who played a royalty herself as Queen Elizabeth; former supermodel Kate Moss and Sophie Turner, more popularly known as Sansa Stark in the "Game of Thrones" TV series.

Meanwhile, "Sherlock" actor Benedict Cumberbatch will be on board the BBC coverage of the Chelsea Flower Show and he's bringing along his mom, Wanda Ventham, BBC America reported.

Wanda Ventham did a cameo, along with husband (and Benedict Cumberbatch's real father) Timothy Carlton Cumberbatch, in the "Sherlock 3" premiere playing the genius detective's real mother and playing the part of helpless parents who want his help for lost glasses.

Maybe viewers can expect some payback time and Wanda Ventham dishing out some embarrassing detail about "Sherlock" actor Benedict Cumberbatch during his awkward childhood and teenage years?