X-Men co-stars and best friends Patrick Stewart and Ian McKellen have taken their bromance to the next level.

The pals locked lips at Wednesday's London premiere of Mr. Holmes. Stewart and his wife, Sunny Ozell, were there to support McKellen, who stars as an aging Sherlock Holmes who comes out of retirement to solve one final case.

McKellen and Stewart's friendship is among the most enduring in Hollywood, with McKellen officiating Stewart's wedding in 2013. In addition to the X-Men films, in which Stewart and McKellen played onscreen rivals Professor X and Magneto, respectively, the pair have collaborated multiple times onstage.

Mr. Holmes hits theaters stateside July 17.