The Queen is said to be “fine” but found the first of four days of celebrations for her Platinum Jubilee “very tiring”.
It was announced on Thursday evening that the monarch would not be attending a service of thanksgiving at St Paul’s Cathedral on Friday.
The 96-year-old watched on television from Windsor Castle instead.
She is believed to have experienced episodic mobility issues during Thursday’s events, which included two balcony appearances for Trooping the Colour and a flypast.
On Friday afternoon it was confirmed by Buckingham Palace that the monarch would not attend the Epsom Derby on Saturday, but as an avid horse racing fan is expected to watch it on television.
At a reception at London’s Guildhall on Friday, the Duchess of Cambridge is said to have told an attendee the Queen is “fine” but had found the day “very tiring”.
Gill Smallwood, from Bolton spoke, with Kate and asked how the Queen was doing.
Ms Smallwood told the PA news agency: “She (Kate) said ‘yes, she was fine, it was just very tiring yesterday, and she (the Queen) had had a lovely, lovely time’.”
She said Kate said Princes George and Louis and Princess Charlotte also “had a lovely time” at Thursday’s celebrations, during which all three Cambridge children appeared on the Buckingham Palace balcony.
Ms Smallwood, chief executive of domestic violence charity Fortalice, was made an MBE in the New Year honours and was among those invited to the St Paul’s service and a reception at the Guildhall afterwards.
She said it had been a “real honour” to be at the service and described it as “absolutely beautiful”.
Asked about the Queen, Ms Smallwood said: “She has just worked so hard for this country and it’s just a real honour to be here today.”
In a statement on Thursday, Buckingham Palace said the Queen “greatly enjoyed” her birthday parade and flypast in London but “did experience some discomfort”.
The palace said that, considering the “journey and activity required to participate” in the St Paul’s service, the Queen had “with great reluctance” concluded that she would not attend.
The monarch did attend a beacon lighting event at Windsor Castle on Thursday evening.
