She was delighted as she shook hands and posed for photographs with Ignazio Cassis and his wife Paola in her Oak Room sitting room.
She stood without her walking stick and was dressed in a blue and grey paisley-style patterned silk dress for the audience on Thursday.
The Queen was wearing her fruit-themed sapphire and diamond grapes brooch which features a sapphire bow and 16 small diamonds shaped like a bunch of grapes.
It was inherited from the Queen Mother.
Buckingham Palace said the sovereign is hoping to attend the State Opening of Parliament in less than two weeks’ time, on May 10 but confirmation is expected closer to the time or on the day.
The Queen has only ever missed two openings in her near 70 year reign.
Organisers on Tuesday revealed details of the London showpiece event to mark the monarch’s unprecedented 70 years on the throne to be watched by an estimated global audience of one billion people.
The Pageant comes at the end of four days of more than 800 events over two Bank Holidays and the weekend.
They include Trooping the Colour and a flypast on Thursday June 2, a Service of Thanksgiving at St Paul’s Catherdal on Friday June 3, and a Platinum Party at the Palace on Saturday June 4.