Oliver Burton's dying wish was to visit Buckingham Palace and have afternoon tea with the Queen.

Unfortunately, Her Royal Highness was unable to fit the 10-year-old into her busy schedule of waving at crowds from afar — so understudy Dame Helen Mirren stepped in to take her place.

Oliver, who has Down's syndrome, has been battling various forms of cancer almost his entire life, and was recently diagnosed with terminal spine and bone marrow cancer.

But last week, for a brief wondrous afternoon, his troubles took a backseat to a meeting with the One True Queen.

Mirren brought Oliver and his family to Gielgud Theatre to see her play the Queen in Peter Morgan's The Audience.

Still dressed as the Queen, she then invited Oliver backstage to have tea and cakes (served by footmen!) and meet her corgis.

Mirren even took the time to knight Oliver, giving him the official title of Sir.

"She stayed in character for the whole thing. Oliver thought she was the real Queen, and well, that's good enough for us," Oliver's father James Browne is quoted as saying.

"It was a pleasure and a privilege to meet such a brave young man," Mirren later told The Sun.

[H/T: ONTD, photos via NC TLC Trust, OLLIE]