"My warmest congratulations to everyone involved in this project," said Her Majesty. "It is a wonderful example of what can be achieved in partnership."
Sir William Barlow's beautiful 1868 train shed glowed green, red, silver and gold as two Eurostar trains and an Olympic Javelin Bullet train rolled gently into the station to enthusiastic clapping from the 1,000 strong audience.
Civil engineering was centre stage throughout the event. Actor Sir Timothy West, appearing as Sir William Barlow, announced to all "I am a consulting civil engineer and this is the station I designed and opened."
The audience was then treated to a detailed explanation of how the structure worked and heard how modern pioneering engineers had created HS1.
One of those pioneers Ian Galloway who was RLE project director and now runs Olympic Delivery Partner CLM said: "St Pancras is absolutely spectacular. To see it rejuvenated makes me very proud."
Contractor Nuttall officially left site last week - the last contractor to leave having also been the first on site at the start of CTRL section two in 2000.
"We are delighted to have been involved in the CTRL project over the past seven years," said Nuttall chief executive Martin Rogers. "The work undertaken has demonstrated our ability to carry out highly complex civil engineering work on time and on budget."
The first scheduled Eurostar services start to use St Pancras on 14 November.