The stone marking Henry VIII's foundation of Dockyard at Deptford has been found behind a false wall at University College London.
The Duchess of Cambridge took part in a nursery rhyme session and played with a frog hand puppet during her visit to a Middlesex hospice.
A boy serving volleyballs at the Duke of Cambridge joked that he "felt sorry" for William after he was unable to return them.
Prince Harry received a pop star reception from young volunteers amid screaming and cheering from fans - but joked that he was sorry for those "who were expecting Harry Styles".
He said: "For those of you expecting Harry Styles, I apologise, and no I am not going to sing."
The prince was a guest at the We Day UK event at north London's Wembley Arena.
He said that Free the Children was a "fantastic" organisation "founded on an inspiring principle - that children have the power to affect change".
The Duke of Edinburgh was given a real taste of Army life with some colourful barrack-room language as he visited the 1st Battalion Grenadier Guards at Aldershot.
Normally, soldiers are on their best behaviour for a royal visit, but one player in a football match could not contain himself from complaining in no uncertain terms how tired he was after being substituted in a game between corporals and guardsmen.
Doubled up in pain and exhaustion on the touchline, the soldier appeared unaware Prince Philip was standing only five yards away as he went through a lexicon of swear words to describe his agony.
"Are you all right? asked the Duke, who was talking to a group of sergeants on the touchline. "No, I'm f*****," said the soldier, still bent double with his head down.
Philip, 92, no stranger to the odd swear word after a career in the Royal Navy, laughed and then continued to chuckle away to himself as the substituted player finally looked up and walked off looking slightly sheepish.
The Duchess of Cornwall will visit the Trinity Hospice in Clapham later.
Trinity Hospice is the oldest hospice in Britain, and provided care to more than 2,500 people with a range of terminal illnesses last year.
Over 450 of those patients were treated at the charity's inpatient center in Clapham.
The Hospice receives just a third of its income from the NHS, and needs to raise more than £7 million every year.
The Duchess of Cambridge has visited a charity project in north-west London. At Northolt High School Kate opened a newly refurbished room that has been transformed into a tranquil art studio and rest space with funds donated by global brokers Icap.
During her visit the Duchess joined a group of nine children who sat at large table in the art room creating still life paintings of pieces of fruit.
Kate, who is the Art Room's royal patron, spent more than half an hour chatting to the six girls and three boys and could be heard asking the youngster if they enjoyed their time in the lesson.
The Duchess of Cambridge's involvement in charities such as the Art Room has "raised its profile undoubtedly", the chairman of the board of trustees said today, after she opened a new art therapy room at a school in West London.
Jo Lloyd Jones, chairman of the Art Room's board of trustees, spoke about the work his organisation does:
We take children at risk of exclusion, who are not coping for a wide range of reasons, and, using art techniques, are able to establish them back into main stream schools, giving them confidence and the ability to cope.
The important thing is she's genuinely interested in what we've done, there's a commitment on her part and we feel very privileged.
The Duchess of Cambridge has arrived at a school in the London Borough of Ealing to open a new art therapy room, as part of an initiative by one of her charities.
Her Royal Highness is a patron of the ICAP Art Room charity and will meet staff and pupils at the Northolt High School.
The Duchess of Cambridge will officially open a new Art Room at a school in Ealing.
Her Royal Highness is a patron of the ICAP Art Room charity and will meet staff and pupils at the Northolt High School later.
A man who walked into a police station and stated that he wanted to kill Prince Harry has been jailed for three years. Ashraf Islam, who's 31 and of no fixed abode, was arrested after making the threat at Hounslow police station in May 2013.
Mr Islam pleaded guilty when he appeared at Uxbridge Magistrates' Court last May, but was only sentenced today.
No weapon was found in a search of Islam's hotel room in Hounslow, where he was staying after flying into the country from Thailand via Hong Kong.
He may be one of our most senior royals, but today one Tottenham toddler just couldn't resist grabbing Prince Charles's nose as he toured the north London borough.
More than two years after it was torn apart by riots, Prince Charles went back to Tottenham to find out how the people living and working there are getting on.
Our Senior Correspondent Ronke Phillips reports.