Queen Elizabeth II has awarded the UK's highest civilian honour to the National Health Service in recognition of health workers' service during the pandemic.
The George Cross, the civilian equivalent of the Victoria Cross for military heroism, comes as the health service marks its 73rd anniversary on Monday.
In a personal message, the monarch praised said NHS staff across the country had worked "with courage, compassion and dedication" for decades.
"This award recognises all NHS staff, past and present, across all disciplines and all four nations," the queen, 95, said.
"Collectively, over more than seven decades, they have supported the people of our country with courage, compassion and dedication, demonstrating the highest standards of public service.
"You have the enduring thanks and heartfelt appreciation of us all."
The Duke and Duchess of Cambridge had been expected to attend a service of thanksgiving at St Paul’s Cathedral, before hosting a "Big Tea" for NHS staff at Buckingham Palace in the afternoon.
However, it is expected only William will attend after Kensington Palace announced Kate will miss her engagements over the next 10 days as she is in self-isolation.
The duchess was confirmed as a close contact of a positive Covid-19 case on Monday morning.
The awarding of the George Cross by the queen is made on the advice of the George Cross Committee and the prime minister.
Prime Minister Boris Johnson, who was admitted to with Covid in April last year, said he had witnessed the courage of health workers on a personal level, saying Britain wouldn't "be where we are today without our health services".
"I know the whole of the UK is behind me in paying tribute and giving thanks for everything the NHS has done for us not only in the last year, but since its inception," he added.
While Johnson's government has routinely praised the efforts of NHS workers, instituting a weekly clap for carers during the first wave of the virus, it has been criticised for offering only a one percent pay rise to staff.
Already under severe strain before the pandemic hit, the NHS has had to contend with one of the worst coronavirus outbreaks in Europe, which has led to over 128,000 deaths in Britain and nearly five million cases.
Professional bodies have warned of severe mental and physical exhaustion in the NHS and a likely exodus of staff if conditions are not improved.
The Royal College of Nursing wants a 12.5 percent pay rise for staff and has warned large numbers of nurses could leave the profession after the pandemic is over.
The Service at St Paul’s will commemorate and give thanks to the NHS’s contribution to the country during the Covid-19 pandemic.
It will reflect on the work and achievements of NHS staff, volunteers and carers, and look ahead to the future of the organisation.
Guests will include leading figures in the NHS pandemic response and several hundred members of frontline staff, patients and others involved in the battle against Covid-19.
They will include NHS chief executive Sir Simon Stevens and May Parsons, who administered the first Covid-19 shot outside of clinical trials.
Also present will be Sam Foster, the nurse who gave the first vaccine from Oxford-AstraZeneca, staff members who treated the first Covid-19 patients in England, and people who have been treated for the coronavirus.