The event was covered live on BBC One, with some viewers spotting Winkleman standing with the royals.
The actor, who is half-sister to Strictly Come Dancing presenter Claudia Winkleman, married Lord Frederick Windsor in 2009, becoming Lady Frederick Windsor.
Lord Frederick is the son of Prince Michael of Kent, one of Queen Elizabeth II’s cousins. He is currently 52nd in line to the throne.
Caitlin Moran, a columnist for The Times, tweeted: “Just watched Prince Charles stand vigil over his dead mother whilst Big Suze from Peep Show looked on. There’s no point in even saying ‘This country is nuts’ any more.”
“Surely a perfect moment for Jeremy, having queued for 12 hours, to shout out how much he’s in love with Big Suze,” joked another person.
“Big Suze being in the royal family is one of the best things about the entire institution,” a third tweeted. “And I can never ever see her at an event without thinking, ‘She was so right to ditch Jez.’”
“OMG Big Suze is at the vigil… looking absolutely flames,” said a fourth.
A fifth tweeted: “Trying to come to terms with #BigSuze being a royal. Mental.”
In the Channel 4 comedy Peep Show, Big Suze is a girlfriend of Jeremy’s (Robert Webb), who David Mitchell’s character Mark Corrigan describes as a “mental posho”. Winkleman has also starred in Sanditon, This Is Going to Hurt, and Two and a Half Men.
Many celebrities have queued to see the Queen lying in state, including Tilda Swinton.
The latest waiting time for the queue is now said to be 24 hours, though there are warnings that entry to the queue may once again be paused if Southwark Park reaches capacity.
Police detained a man at about 10pm on Friday (16 September) after he reportedly moved out of the queue to approach the Queen‘s coffin, leaving several inside Westminster Hall shocked.
It happened just a few hours after the Vigil of the Princes, with King Charles III and his three siblings holding a 15-minute vigil beside their mother Queen Elizabeth II’s coffin.