Donald Trump with Keith Schiller, who has quit the White House after losing his ‘walk-in’ privilege to see the president

The name Keith Schiller is barely known, even in Washington, where he occupies the nebulous-sounding role of director of Oval Office operations. But his imminent departure — another casualty of the tough new regime in the White House — has left Donald Trump uncharacteristically reflective and almost bereft.

While the president has weathered the departure of a number of key aides, including his chief strategist Steve Bannon, arguably none was as important as Schiller.

For the past 18 years he has been Trump’s chief security officer and gatekeeper and a constant presence at his side. He has been described as the president’s “wing man”, his “emotional anchor” and even his “security blanket”. Others view him as Trump’s enforcer, one of the few people he really