The King has urged the nation to reflect on the “extraordinary courage and compassion” shown in the wake of the 7 July bombings on the 20th anniversary of the attacks.
In a message marking two decades since the atrocities, he highlighted the “spirit of unity” that emerged in London and across the country, which has aided national healing, he said.
On 7 July 2005, four suicide bombers targeted the capital’s transport network, killing 52 people and injuring over 770 across three underground trains and a bus.
The monarch called for a renewed commitment to fostering a society of all faiths and backgrounds, standing firm against those who seek to sow division.
He said: “Today, as we mark 20 years since the tragic events of 7 July 2005, my heartfelt thoughts and special prayers remain with all those whose lives were forever changed on that terrible summer’s day.
“We remember with profound sadness the 52 innocent people who were killed in senseless acts of evil – and the enduring grief of their loved ones.
“We recall, too, the hundreds more who carry physical and psychological scars, and pray that their suffering may ease as the years pass.
“In doing so, we should also remember the countless stories of extraordinary courage and compassion that emerged from the darkness of that day.
“The selfless bravery of our emergency services, transport workers, and fellow citizens who rushed towards danger to help strangers reminds us of the very best of humanity in the face of the very worst.”
Other members of the royal family are to join services and memorials to mark the anniversary.
On behalf of the King, the Duke and Duchess of Edinburgh will attend the National Service of Commemoration at St Paul’s Cathedral from 11.30am on Monday.
The King also stressed the importance of communities coming together in times of adversity.
He said: “While the horrors will never be forgotten, we may take comfort from the way such events rally communities together in solidarity, solace and determination. It is this spirit of unity that has helped London, and our nation, to heal.
“As we remember those we lost, let us therefore use this 20th anniversary to reaffirm our commitment to building a society where people of all faiths and backgrounds can live together with mutual respect and understanding, always standing firm against those who would seek to divide us.”
