One of David Cameron's close allies, Sir Oliver Letwin, said his knighthood was "bitter- sweet" as he defended the former prime minister against accusations of cronyism.
The former Number 10 policy chief was awarded the title in Mr Cameron's resignation honours list, which included gongs for a string of political supporters, Conservative Party donors and Downing Street staff.
He made the comments after being formally knighted by the Queen in a ceremony at Windsor Castle on Friday.
Sir Oliver served in the Cabinet Office and then as chancellor of the Duchy of Lancaster until he was axed by Theresa May in a Cabinet shake-up when she replaced Mr Cameron as Prime Minister following the EU referendum.
Sir Oliver, who was accompanied by his wife, Isabel, and daughter, Laura, said receiving the honour had been a "surreal experience" but the ceremony was "rather fun".
He said: "Of course, in my case, it arose in combination with leaving government so it was an interesting, bitter-sweet experience. But I'm very grateful to David Cameron for nominating me.
"I think it's inevitable when an outgoing prime minister has an honours list there will be critics of it - I can't remember an occasion when there weren't such criticisms made.
"I think, in the end, having a system in which the people who serve a prime minister receive some recognition - not people like me, politicians, but the people who are working invisibly in very high-pressured environment of Number 10 - I think it's right that they should be recognised in some way."
Sir Oliver added that he understood why Mrs May sacked him and he backed the Government's post-Brexit vote plan.
The 60-year-old said: "Theresa was gracious, we've worked together for 17 or 18 years. She had a very clear and understandable plan to create her own Government in a different shape and that I completely understand.
"I think, actually, she's been doing a fine job in very difficult circumstances."
The West Dorset MP, who also once served as an adviser in Margaret Thatcher's Number 10 policy unit, plans to retire as an MP in 2020 and said he is looking forward to writing books and forming a new think-tank.
Sir Oliver was joined at the investiture ceremony by actor Brian Blessed, who collected an OBE for services to art and charity.
The 79-year-old has enjoyed a long career on stage and screen stretching back six decades, and is best known for his roles as Prince Vultan in Flash Gordon and Augustus Caesar in I, Claudius.
Speaking after collecting his award from the monarch, he praised her as "the finest Queen we've ever produced".
He added: "I find her always an enchanting professional, she's utterly professional.
"She does have something special. She does have an extraordinary inner beauty and grace and that's what I felt just now."
He revealed he spoke to her about her son Charles, who he works with as an ambassador for the Prince's Trust, and said he made the Queen "beam with pride".
He has also raised money and supported animal welfare charities, including the Born Free Foundation.
Blessed, who was among a host of celebrities to sign a letter urging the UK to stay in the EU, said his reason for doing so was for "artistic" reasons rather than economic.
He said: "My attitude wasn't even political, it's quite simply that we are Romans, we are Anglo-Saxons, we're Celts, we're Gauls... We're European.
"I just feel a huge affinity, they're very much our heart and soul."
He also hit out at US presidential candidate Donald Trump, calling him an "idiot".