The actor playing role in《Sherlock Season 3》is“Mark Gatiss”

Sherlock's brother, a senior British government official (MI6).

He has a relatively cold relationship with Sherlock, but in fact he still cares about his smart but rebellious brother. He initially wanted to bribe Watson to spy on Sherlock but was rejected, so he secretly placed protection personnel around Sherlock and Watson.

But when Sherlock did something outrageous, Mycroft still felt like he hated iron.