Queen knights Captain Sir Tom Moore in rare outdoor ceremony hours after Princess Beatrice's wedding

Queen Elizabeth has knighted Captain Sir Tom Moore in a rare outdoor investiture ceremony in the quadrangle of Windsor Castle.

Her Majesty performed her first face-to-face royal engagement since the coronavirus crisis began in March, just hours after watching her granddaughter Princess Beatrice marry Edoardo Mapelli Mozzi at The Royal Chapel of All Saints at Royal Lodge, Windsor.

The 94-year-old monarch used her father George VI's sword to confer the insignia of Knight Bachelor to the 100-year-old WWII veteran in the glorious sunshine.

Captain Tom, as he's become affectionately known in the UK, won the attention of the world during lockdown when he raised over £32 million ($57.5m) for NHS coronavirus relief.

The then 99-year-old set out to raise £1000 ($1800) by completing 100 laps of his garden ahead of his milestone birthday on April 30. His efforts won him fans globally and that tally soon rose very quickly.

"Thank you so much. An amazing amount of money you raised," the Queen told Captain Tom.

RELATED: Duchess of Cornwall praises Captain Tom Moore on his 100th birthday

Captain Tom was joined at the ceremony by his daughter Hannah Ingram-Moore, son-in-law Colin Ingram, grandson Benjie and granddaughter Georgia.

Her Majesty spoke to all of them after the official duties were done, as they gathered around the man of the moment.

"It was an absolutely outstanding day that you could never, ever believe before 100 that I was ever going to get such an honour as I have today," Captain Tom told reporters after the ceremony.

Proudly posing with his new medal, the centenarian said he felt "privileged" to have the chance of meeting and speaking with Her Majesty.

Ahead of the ceremony, Captain Tom said via his family on Twitter: "Good Morning! Ready and raring to go for what is a very special day. Thank you for all the well wishes, as ever, overwhelmed by your support."

When news first broke that the Queen would perform the investiture herself, he couldn't quite believe the honour.

"I could never have imagined this would happen to me," he said via Twitter, adding: "It is such a huge honour and I am very much looking forward to meeting Her Majesty The Queen. It is going to be the most special of days for me"

Camilla, Duchess of Cornwall commended his efforts on his birthday, saying: "That wonderful man, Captain Tom, walking around and raising all that money, that sort of thing makes you proud to be British, doesn't it?"

Captain Tom received an RAF flyover, a birthday card from the Queen and the monarch also upgraded his rank to Honorary Colonel.

"This morning @LLieutenantBeds, The Queen's personal representative in Bedfordshire, delivered a birthday card to @captaintommoore from Her Majesty," the Royal Family shared on Twitter at the time.

"Today we join people across the UK and around the world in wishing Captain Tom Moore a very happy 100th birthday," they added.

His knighthood award was formally announced by Downing Street on Wednesday, May 20.

"I am absolutely overwhelmed," Captain Tom said at the time.

"Never for one moment could I have imagined I would be awarded with such a great honour. I'd like to thank Her Majesty The Queen, the Prime Minister and the Great British public. I will remain at your service.

"This started as something small and I've been overwhelmed by the gratitude and love from the British public and beyond. We must take this opportunity to recognise our frontline heroes of the National Health Service who put their lives at risk every day to keep us safe."