People across the UK have observed a minute's silence to remember victims of the pandemic on the anniversary of the UK's first lockdown.
The Queen has reflected on the "grief and loss felt by so many" as she led tributes, sending a message to the hospital where the Duke of Edinburgh had heart surgery.
"As we look forward to a brighter future together, today we pause to reflect on the grief and loss that continues to be felt by so many people and families, and pay tribute to the immeasurable service of those who have supported us all over the last year," the Queen said.
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The note, along with the bouquet of irises, tulips, mixed narcissi and ranunculus, was carried to St Bartholomew's Hospital in the city of London from Windsor Castle, where the Queen and Prince Philip have been staying during the pandemic.
Across the country, Britons marked the anniversary of Boris Johnson's first lockdown with a minute's silence in memory of those who have died during the pandemic.
MPs and peers in both Houses of Parliament and ministers in the devolved nations marked the anniversary at midday, while cathedrals in Blackburn, Winchester, Gloucester and York Minster also fell silent.
NHS and social care workers also joined the pause for reflection.
At 8pm people are being encouraged to stand on doorsteps with phones, candles and torches to signify a "beacon of remembrance".
The London Eye, Tate Britain, Blackpool Tower, the Scottish Parliament, Belfast City Hall and other landmarks will be lit in yellow on Tuesday evening to mark the occasion.
A year since his dramatic "stay at home" TV address to the nation, the prime minister said the past year has been one of the most difficult in the country's history.
And it comes on the day new figures from the Office for National Statistics showed a total of 149,117 people have had COVID-19 recorded on their death certificate since the pandemic began.
Marking the anniversary, Mr Johnson said: "The last 12 months has taken a huge toll on us all, and I offer my sincere condolences to those who have lost loved ones.
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"Today, the anniversary of the first lockdown, is an opportunity to reflect on the past year - one of the most difficult in our country's history.
"We should also remember the great spirit shown by our nation over this past year.
"We have all played our part, whether it's working on the front line as a nurse or carer, working on vaccine development and supply, helping to get that jab into arms, home schooling your children, or just by staying at home to prevent the spread of the virus.
"It's because of every person in this country that lives have been saved, our NHS was protected, and we have started on our cautious road to easing restrictions once and for all."
Labour leader Sir Keir Starmer was among those who joined the minute's silence to remember those who have lost their lives.
Earlier, he tweeted: "As we mark one year since our country entered the first lockdown, my thoughts are with all those who have lost loved ones since the pandemic began."
First Minister Nicola Sturgeon told the Scottish Parliament: "A year ago today we all felt scared and uncertain - we did not know exactly what lay ahead or how long it might last.
"But we did know we had to come together to save lives and I know I will never be able to adequately express the depths of my gratitude for all the sacrifices that have been made by so many over the past year."
She added: "I think all of us have really struggled in the past year with the paradox this virus has created.
"We've had to stay physically apart from each other, from those we love most, at a time when we have never needed each other more.
"None of us though should be surprised that this year has been filled with difficulty and anxiety and, for too many people, with grief.
"But I think we can and should also take some heart from the extent to which it has also been filled with compassion and love."
Northern Ireland's Deputy First Minister Michelle O'Neill said balancing the need to protect lives and livelihoods had been a "nightmare".
"I think there'll be plenty of time for reflection, I think today is about individuals, their loss, their experience and we're focused on that," she said.
Lockdown: One Year On is a special programme marking the anniversary of the first national lockdown on Sky News at 7pm tonight
