The “We Do Not Consent!” mass rally is protesting government implemented restrictions to combat covid and bills the slogan “Human race, get off your knees.”
Icke’s son, singer-songwriter Gareth Icke, 38, is also guest speaking.
A further event, planned to take place in Hyde Park on Sunday, is billed as a “people’s network and family picnic.”
The Met have prepared for a “significant policing operation” to deal with the demonstrations in Trafalgar Square and Hyde Park today.
In a statement, they said violence will not be tolerated and throughout the week they have been “engaging with organisers, reminding them of their legal obligations.”
They added: “However, if people fail to comply, and continue to put themselves at risk, officers will take enforcement action.”
Protest is an exemption from the rule of six restriction but those attending the event have been told to remain socially distant.
Today’s event follows a separate rally by anti-lockdown protestors last week in London which led to more than a dozen officers being injured and 32 arrests were made.
Commander Ade Adelekan, who is leading the Met operation today, said: “Last weekend it was highly disappointing to see that a small minority of demonstrators targeted officers with violence.”
He added: “I will not tolerate a repeat of this behaviour this weekend and officers will respond quickly to any scenes of violence.”
Last week’s event saw anti-vaxxers holding banners while chanting “freedom”, “covid is a scam” and “save our rights. No mandated vaccines.”