Tens of thousands of pro-Palestinian demonstrators have joined a march in central London calling for a permanent ceasefire in the Israel-Gaza conflict.
Demonstrators are marching on the second day of a four-day pause in fighting between Israel and Hamas.
It is the first London march since Armistice Day, when more than 100 counter-protesters were arrested.
On Friday, police said they would issue leaflets warning people about words or images that could break the law.
The Metropolitan Police has been under pressure for weeks over its handling of the now-regular demonstrations, with pressure from senior politicians for officers to come down harder on alleged displays of antisemitism.
Some 1,500 officers will be on the streets on Saturday with instructions to protect war memorials following criticism that police have not stopped protesters climbing on them.
The force has also said it is planning to position Arabic-speaking officers on the march, backed up in its central control room with lawyers to advise on whether specific phrases break the law.
Shortly after the march began, the Met said it had arrested a man who was spotted carrying a placard with Nazi symbols on it on suspicion of inciting racial hatred.
Protesters carrying Palestinian flags were seen with placards demanding a permanent ceasefire in the conflict, while some referenced the slogan "from the river to the sea".
The language is interpreted by Israel and most Jewish groups as an expression of a desire to see Israel erased from the world, though pro-Palestinian activists contest this, saying it refers to "the right of all Palestinians to freedom, equality and justice".
The temporary truce is still holding and follows weeks of fighting and Israeli bombardments of Gaza, with the conflict sparked by the Hamas incursion into southern Israel that saw 1,200 people killed.
Speaking at London's march, a pro-Palestinian protester played down the long-term significance of the temporary ceasefire.
Shaun, 33, from north London, said: "I don't know what's going to come from it, I don't know if it's positive, but I know full well that once this truce and temporary ceasefire are done they (Israel) are going to continue bombing and we're going to be right back where we were, so I'm not holding my breath."
Organisers have said at least 100,000 could turn out for Saturday's protest in London, which is marching from Park Lane to central London. Marches are also being held in Glasgow and Cardiff.
Asked about the Met's leaflets, marchorganiser Ben Jamal, director of the Palestine Solidarity Campaign, said police had been placed under "considerable pressure" by politicians to be more aggressive in their policing of the demonstration.
"The leaflets reassert what everybody knows, which is that there are laws against hate speech, there are laws for showing support for proscribed hate organisations - so I'm not sure what the leaflets add," he said.
Separately, the afternoon also sees a different protest by the Islamist group Hizb-ut-Tahrir outside the Egyptian embassy.
It is the first by the group since 21 October, following an outcry when video emerged showing a man chanting "jihad". The Met found no offences were identified from the clip.