Britain observed a minute’s silence on Friday as part of an official day of mourning for the tourists killed in a massacre on a Tunisian beach last week.
Flags flew on official buildings at half-mast, and people across the country stopped what they were doing at midday to think about those killed by a gunman in the deadliest terror attack on Britons in nearly a decade.
In Sousse, the British ambassador, Hamish Cowell, joined diplomats from other countries whose citizens were killed and Tunisian dignitaries to lay wreaths on the sand at the scene of the attack.
Seven days ago Seifeddine Rezgui walked on to the beach at the El Kantaoui resort and opened fire.
He killed 38 people - including 30 UK nationals - before police gunned him down.
Three Irish nationals, two Germans, one Belgian, one Portuguese and one Russian were among the dead.
The bodies of 17 British victims have been repatriated since Wednesday, all flown to RAF Brize Norton.
More were expected to return on Friday and Saturday. Wounded Britons - including four with severe injuries - have already been brought back to the UK.
David Cameron, the prime minister, had asked all government departments and official buildings in the UK, as well as embassies and military bases across the world, to fly their flags at half-mast for the day.
Local authorities, police forces and schools were asked to observe the silence. In train stations, posters were put up and announcements made to remind passengers and staff.
The Queen paid her silent tribute at Strathclyde University, Glasgow, where she was opening a new innovation centre. The royal party was touring the Institute for Future Cities when an announcement was made on the public address system.
Outside Buckingham Palace, London, the band stopped playing in the middle of the changing of the guard.
Union flags flew at half-mast at royal residences across the UK.
However, at Holyrood House the royal standard flew in recognition of the Queen being in residence.
Crowds and competitors fell silent at Wimbledon, Henley regatta, the British Grand Prix and the horse races in Doncaster, Newton Abbot, Sandown, Beverley and Haydock.
The government also contacted faith leaders to encourage their congregations to join the country in remembrance.
On the sand outside the Imperial Marhaba hotel, where most of the tourists died, security was tight ahead of the beachfront ceremony.
The sands were criss-crossed by police on horses and quad bikes. A coastguard cutter was stationed offshore.
Mr Cowell was joined by a representative of the Tunisian government to lay wreaths around a spot where improvised memorials have continued to grow. Half a dozen had already been scooped out of the sand and arranged around a large heart-shaped depression, surrounded by flowers, candles and notes from well wishers.
At midday, the dignitaries there fell silent to join the period of remembrance taking place across the UK.
The Muslim Council of Britain has urged British Muslims to make their voices heard to pray for peace, and speak out against terrorism, and has called on mosques and imams to deliver a sermon of peace at Friday prayers, to remind people “that these killers do not respect the sanctity of life as laid down in Islam”.
It is believed Rezgui — who was shot dead by police — had accomplices who helped him to carry out the atrocity and the Tunisian government said it had made a number of arrests.
Eight people — seven men and one woman — were in custody, suspected of having direct links to the massacre, but four others had been released, government minister Kamel Jendoubi said.
He said the investigation “has allowed us to discover the network behind the operation in Sousse”.
According to Tunisian officials, the gunman trained at a Libyan jihadist camp at the same time as the two gunmen who attacked the Bardo museum in Tunis in March, killing 22 people.
Defence secretary Michael Fallon vowed that those responsible for the massacre would be "tracked down".
The Metropolitan Police said 76 family liaison officers across the country were supporting the families of those killed and the survivors while hundreds of counter terrorism officers were helping the international response to the attack.
Specialist advisers have also been deployed to Tunisia by the National Policing Counter Terrorism Headquarters to assist the Foreign Office and Tunisian authorities in reviewing security at other tourist resorts and attractions.
Assistant Commissioner Mark Rowley, the national policing lead for counter terrorism, said: "With the threat level to the UK from international terrorism remaining at severe, the UK police service is continually reviewing security to help ensure people and places are as safe as possible."