At 11.31am on Saturday, the first rendition was heard, drowning out the double-decker buses circling Marble Arch. Several dozen protesters had begun urgently chanting the controversial slogan, “From the river to the sea, Palestine will be free”. Three metres away, a pair of officers from the Metropolitan police’s territorial support group looked on impassively. The crowd grew quickly; hundreds started singing the slogan. Two blond-haired children holding Palestinian flags joined in, their parents beaming proudly. Among those singing at the latest pro-Palestinian protest in central London was fashion student Jenny Herman, who said: “The chant is simply a call for freedom. It’s about giving Palestinians their human rights.” In the eyes of the home secretary, however, Herman is an antisemite. Last week, Suella Braverman intervened on the issue, saying it is “widely understood” that the chant calls for the destruction of Israel. Tensions over the song’s true meaning escalated further on the eve of the protest after Jewish groups including the Board of Deputies, Jewish Leadership Council and the Community Security Trust asked prosecutors to clarify whether chanting the slogan is a criminal offence. Scotland Yard said they were unlikely to arrest those who chanted the slogan at the march, knowing that this would mean detaining thousands, some of whom see it as innocently calling for Palestinian self-determination. Holding a clenched fist in the air, Syrian-American Heidi Affi, took instant offence when asked if she though the slogan antisemitic. “It’s absolutely not a slur, not a terrorist threat. It’s a cry for freedom, for Christians, Jews and Muslims to live together.” Born in Milwaukee, Wisconsin, the 28-year-old added: “It’s just not about ethnicity.” Nearby, stylist Alia Nusseibeh said she was at the protest simply to take a stance on human rights issues in Gaza. Nusseibeh, also 28, whose father is Palestinian, added: “Our government is not supporting human rights, it wants to keep the status quo.” Behind her, a man led a fresh chorus of the “river to the sea”. Would she join in? “Of course – it’s simply a call for freedom within that land.” Teacher Philip Grayson seemed incredulous when told the slogan he had been singing moments earlier had been labelled antisemitic. “Really? I genuinely had no idea.” The 47-year-old added: “I hated [Jeremy] Corbyn for how he behaved on this issue.” By 1.30pm, as the rain began easing, the crowds were still assembling, streaming down Oxford Street and Edgware Road towards Marble Arch and, from there, on towards Downing Street. The sheer volume of late arrivals meant the police revised an estimated turnout of 70,000 to “up to 100,000” as of 2pm. Along the route, staff in shops were seen holding sheets of A4 paper with “Free Palestine” handwritten on them while local residents leaned out of windows to join in the chanting, with some banging pots and pans. Elsewhere in the throng, student Rubina, 20, said attempts to “demonise” protesters were shameful and – to her and her friends – the slogan advocated a two state-solution, a call for the idea of establishing an independent Palestinian state side-by-side with Israel. “It is calling for the Palestinians to coexist, to live as normal human beings – even animals have access to food and water,” she added, referring to the siege of Gaza. Even as the rain returned in the late afternoon, the crowd remained good-natured, with 1,000 police deployed in an attempt to avoid a repeat of scenes the previous Saturday when protesters were seen stamping on an Israeli flag and others taped pictures of paragliders to their jackets in apparent homage to Hamas gunmen involved in the killing of more than 1,400 Israelis. Such scenes had prompted demands, including from Lord Pickles, special envoy for post-Holocaust issues, for Saturday’s march to be called off, following the lead of France and Germany which have banned pro-Palestinian demonstrations in the wake of the Hamas attacks. The organisers of the main march had also drawn close scrutiny in the run-up to the march after the Jewish Chronicle reported that the leaders of several groups behind the recent protests had links to Hamas or had expressed support for the terrorist organisation. Shop worker Angela Braithwaite, 57, dismissed the claims as “smears”. The 57-year-old Londoner said: “This march is not a pro-Hamas march, it’s about starving children.” Ruhal Tarafder had arrived with his family to register “disgust with the UK government and its complicity in war crimes”. The 49-year-old said he was happy not to sing “From the river to the sea” if it offended the Jewish community. “It’s not a problematic term for me, but if people have a problem with it, then there are millions of other things that could be sung.” His two children were more preoccupied with stopping the killing. Five-year-old Ibrahim – barely audible over the roar of a police helicopter – pleaded: “Let Gaza live.” His brother Salahadeen, seven, shared a similarly pithy message for global politicians: “I just wish they would debate more.”