The Queen made a hilarious quip after she saw the funny side when a man's mobile phone rings at a crucial moment.
The 96-year-old monarch, joined by the Princess Royal, was making a rare public appearance outside Windsor Castle, to formally launch the new home of the £22 million Thames Hospice.
Just as she was introduced to Graham White and his wife Pat, who has stage 4 cancer and is receiving respite care at the centre in Maidenhead, his phone rang.
His embarrassment was short lived when he quickly reached into his pocket to turn it off.
However, The Queen brilliantly quipped: "Typical, a phone goes off immediately", and Graham sheepishly said it was his son ringing.
Pat sat as she chatted to the Queen, who stood and leaned on her now familiar walking stick, and afterwards the 63-year-old described the encounter as "very emotional", adding: "This is a memory that I will treasure."
She joked about her husband's phone ringing, saying: "I could have killed him! People think the Queen is all stiff upper lip but she has a sense of humour."
Graham, 67, from Sandhurst, Berkshire, said: "I turned my wife's phone off and I could have sworn mine was off - that was a bit embarrassing."
His wife said: "The Queen said the building is beautiful and she showed a keen interest in the different treatments for cancer, and hoped the new building would help support all the cancer patients here.
The former Windsor site of Thames Hospice was opened by the Queen in 1987 and past visitors have included Diana, Princess of Wales, and Sophie, Countess of Wessex.
Now sited beside a picturesque lake surrounded by trees in nearby Maidenhead, the hospice's new building features an open plan reception with an airy atrium, a cafe and a shop.
Pat and her husband served in the Army, with Graham, a former Warrant Office Class 1, working as a functions manager at the Royal Military Academy Sandhurst when the dukes of Cambridge and Sussex were training to be officers.
She said about the hospice: "When you arrive and walk through the car park, you can feel the love. I come here for yoga, to do crafts. For me, everyone here is like an extended family."
Her husband added: "People have visions a hospice is somewhere you come to die - it's not like that here."
The Queen's visit was her fourth to the hospice in its 35-year history and she also met volunteers, medical staff and supporters of the vital service, which provides palliative and end-of-life care and support to people across East Berkshire and South Buckinghamshire.
Sarah Williams Kelly, a former nurse who is now a volunteer at the hospice, chatted to the Queen and said afterwards: "She said how lovely the building is and asked me about my role looking after patients and relatives."
Local MP and former prime minister Theresa May is a supporter of the centre and joined the other guests.
Jonathan Jones, chairman of the hospice's trustees, paid tribute to the Queen for her 70-year reign and she smiled warmly as she received a round of applause.
Jonathan told the gathered guests: "We are particularly thrilled, ma'am, in this exceptional Platinum Jubilee year, you are here today, and I'm sure everyone will join in congratulating you on this amazing milestone and for your 70 years of service to the country."
The Queen left after signing the visitor's book, while Anne stayed to visit hospice patients in the 28-bed inpatient department.
The hospice's chief executive, Debbie Raven, said: "To know the royal family and especially the Queen are interested and are looking out for us means so much, not just to us but to our patients."
