Hundreds of white paper angels, each representing an innocent child who has been killed in the war in Ukraine, hung above political and faith leaders who had gathered in London to pray for peace.

The haunting image reflecting the human cost of Russia’s year-long invasion formed the backdrop to an interfaith service attended by former prime minister Boris Johnson, London mayor Sadiq Khan, dignitaries and members of Ukraine’s scattered community.

Thoughts were given to those who have been forced to flee their homes, have lost family and friends and who are sick with worry for loved ones in Ukraine at the sombre service at the Ukrainian Catholic Cathedral.

Loud applause broke out as Mr Johnson, who had watched intently from the front row and was an early international supporter of the eastern European nation, had to leave the service early.

Mr Khan told those gathered that Russia must pay for its crimes and aggression, the international community could have acted quicker to help and that Ukraine’s “valour inspired the world”.

He said: “One year ago, Ukraine was threatened by tyranny. The future of your nation was uncertain.

“Your borders were breached and many of your cities encircled.

“It looked like all hope was lost, but then something remarkable happened – Ukrainians didn’t roll over, you resisted.

“Orthodox Christians, Jews, Catholics, Muslims and men and women of other faiths all stood together, united under one flag and by one unshakeable belief…

“A belief that all Ukrainians have the right to choose their own destiny.

“Your valour inspired the world.”

Mr Khan, who said that “London stands with you”, also reflected that “nations pulled together – like never before – with sanctions, aid and weapons but no-one should make the mistake of thinking Ukrainians owe us anything”.

He added that “it’s us who owe Ukrainians everything” as “a threat to your democracy is a threat to our democracy”.

Mr Khan said: “For too long – and to our collective shame – the actions of your aggressors were met with inaction.

“As a country, we allowed our homes, businesses and football clubs to be bought and used to launder ill-gotten gains.

“And the cost of our complacency would eventually be paid by ordinary Ukrainians.

“It should never have taken your suffering to act.

“On this tragic milestone, I call again on the Government to decisively rid our capital and country of illicit finance and never again allow London to become a haven for corrupt wealth.”

He added: “For every village, town and city your heroes liberate, more evidence of unspeakable atrocities is uncovered.

“The individuals responsible for these wicked acts must be held to account, but that alone isn’t enough.

“All efforts must be made to ensure Russia pays reparations for the lives lost and damage done, and that (Russian President Vladimir) Putin – and his acolytes – are made to answer for their crimes in a court of law.

“Some say there’s no chance of success, but one year ago many said Ukraine had no chance of success – and look where we are.”

Children from St Mary’s Ukrainian School, many wearing yellow T-shirts, could be seen holding candles as prayers were offered by a range of faith leaders and hymns sung.

These included good wishes for Ukraine’s President Volodymyr Zelensky and his supporters.

In a message of solidarity posted on Thursday, Archbishop of Canterbury Justin Welby said: “The Russian decision to invade Ukraine was a monumental act of evil.

“Only by supporting Ukraine can we hope to build a lasting and just peace.”