Four-year-old Hannah Terrill's dream came true when she came face-to-face with the Queen today.

Little Hannah, of Mably Grove, Wantage, presented the Queen with a posy containing red roses during her visit to the £260m Diamond Light Source laboratory at Harwell, near Didcot.

Hannah, who has just started in reception at Wantage Primary School, was dressed in a ruby red dress that matched the Queen's outfit.

Beaming from ear to ear, Hannah said: "I liked meeting the Queen - I was very excited and now I feel very happy."

She was specially chosen to present the Queen with flowers as she was the first child among Diamond Light Source staff to be born.

Tonight, her mother Celia said: "We are all very proud of her and everybody has been making a fuss.

"Hannah was quite excited and she had a new dress especially for the occasion. She behaved very well and was relatively calm - although she's quite tired now.

"It's half term next week. She's looking forward to telling her friends all about it when she gets back."

Accompanied by the Duke of Edinburgh, the Queen officially opened the laboratory's 'super microscope' - which is 10 billion times brighter than the Sun - at a ceremony attended by hundreds of guests.

Dressed in ruby-red, the Queen toured the giant machine, which covers an area more than three times the size of Buckingham Palace and half a kilometre in circumference.

The centre represents the largest investment in UK science in more than 40 years.

The Queen was told how the powerful light will enable scientists to understand the early solar system, conserve ancient artefacts such as the Tudor warship Mary Rose, and develop drugs to fight diseases such as cancer.

Prof Gerd Materlik, chief executive of Diamond Light Source, said: "We feel extremely honoured by the Royal visit, which not only marks our official opening but also pays tribute to all those involved with the design, construction and operation."

Hannah's scientist father, Nicholas, said: "The Queen was very interested in the work we do because there are a huge amount of historical records, such as the Dead Sea Scrolls, which we will be able to understand, because of the technology."

Scientist Thomas Sorensen added: "We had to build something this size to be able to study something as small as a flu virus.

"I think it's brilliant we can show the Queen what we do, which is to literally shed light on things."

After lunch, the Queen unveiled a sculpture and a plaque commissioned by Kent sculptor Paula Groves to mark the official launch of the facility.

Chilton Primary School pupils waved as the Queen left, and sky divers from the Red Devils dropped from the sky on to the site.