Tens of thousands of people have gathered in central London to express solidarity with the people of Ukraine, with the consensus among the vast crowd being that the embattled country would prevail in the war against Russia. After the rallying call by Ukraine’s president, Volodymyr Zelenskiy, for people everywhere to protest against the bloodshed by taking to the streets, Trafalgar Square was transformed into a sea of yellow and blue. The London mayor, Sadiq Khan, who organised the march, said Ukraine had endured “unimaginable pain and suffering” over the past month. Khan, who acted after Zelenskiy’s call for global support, said London stood “shoulder to shoulder with Ukraine in its darkest hour”. On their route through London, demonstrators marched beneath Yoko Ono’s Imagine Peace message on a huge electronic billboard in Piccadilly, many waving the yellow and blue of the Ukrainian flag as they passed. Ono sent a message to the thousands assembled, stating: “Remember, we are all family. Power is peace.” The shadow foreign secretary, David Lammy, then sent a chant of “Stand with Ukraine” reverberating around the historic landmark. Yet the biggest cheer was reserved for Zelenskiy, when his call to unite in rallies and stand for freedom was played on a large screen. Among those gathered was Izyma Savkina, who fled Ukraine’s capital, Kyiv, last week. The 36-year-old said: “Eventually the Russians will kill Putin themselves. But in the meantime we need more air support and more weaponry from Nato.” Elsewhere, friends Yuliya Gavnylyuk, from Ivano-Frankivsk, and Sofia Silina, from Zaporizhzhia, also believed their country would ultimately win the war. “Absolutely, we will win. We are fighting for our freedom and for our homes,” said Gavnylyuk. Silina added that three of her family’s homes had been destroyed in the fighting and all they had left was their grandfather’s house, which he now guarded alone with a gun close to the frontline. When the conflict is over, they said, they will travel back to Ukraine for a huge party. However, British imam Mansoor Clarke cautioned politicians to ensure that the conflict did not escalate into a world war. “We need less sabre-rattling to ensure there is less chance,” he said. Uliana Loseva said that until the conflict was over, she would not be able to sleep. “My mother is in Lviv and every time I call her I don’t know if she’s going to pick up.” As another day of fighting 1,600 miles to the east continued, Hanya Dezyk, from the Association of Ukrainians in Great Britain, which has 3,000 members in community centres around the UK, said the world’s perception of Ukraine had changed profoundly since Putin invaded. She said: “Previously, Ukraine was a bit hidden, but now everybody knows that we are looking to Europe and we are not going back to Soviet times, Russian imperialism.” Celebrities were spotted offering their support. Among them was the actor Helen Mirren, who offered her thoughts to Ukraine during “this terrible time”. The actor added: “It’s important that we send a message of support so that Ukrainians know that they are not alone, and I’m proud that the people of London are standing together in their name this Saturday.” Julie Walters was another. She said: “It’s important that the world unites to show them that they have our support in their time of need, and I’m so glad that London is joining as one to send a message of solidarity loud and clear.” Khan, who also announced more than £1.1m in funding to support refugees and people seeking asylum in London, added: “We have a proud history of providing sanctuary to those fleeing conflict, and this funding will ensure that support is there to help in their time of need.” The mayor said the money would help people affected by the invasion of Ukraine, as well as European Londoners, the Windrush generation and those hit by the lack of capacity in the asylum system. Anna Bird, chief executive of the European Movement, added: “It’s time to unite across parties, organisations, faiths, beliefs and backgrounds to condemn this act of Putin’s aggression. Our duty is rooted in a belief that a closer, more united and peaceful Europe is in all of our interests.” Since Zelenskiy’s call for the world to show their support for his embattled country, sizeable protests have occurred in the Netherlands and Ecuador and cities including Bulgaria’s Sofia, Krakow in Poland and Mexico City.