It was a demonstration with a curious ambition: to be invisible.

On Tuesday, nearly 500 anti-Zionist strictly Orthodox Jews staged a mass protest outside the Israeli Embassy, complete with loudspeakers and a sea of banners. The "True Torah Jews" had sent two long press releases and phoned the JC to alert us of their intention to demonstrate against plans to build on an ancient burial ground in Israel.

I arrived to find organisers bellowing at passing shoppers as police cordoned off pavements for several hours in Kensington's busy High Street. One shouted: "Let our Sages rest in peace!" and another: "Mr Ambassador, you have gone mad!"

But the protesters were less than happy when I approached. First they were distressed that the JC was reporting on their event at all. Then an organiser complained: "The Jewish Chronicle should not have sent a woman."

Some even refused eye contact with a female reporter - even though I was modestly dressed head to toe - and others turned their backs in protest. When a female passerby confronted a protester, saying: "Israel has enough problems! You are not Jews!", the man covered his ears and ignored her.

To speak to an organiser, I had to use a male intermediary. The owner of Mesoiroh Books would not speak to a reporter, although he was ready to pose with his banner for photographs.

One man who did speak, solicitor Geoffrey Niman, said: "I came here to register my protest against the disregard of the sanctity of human remains. It is fundamental to the Jewish religion that human remains don't enter oblivion, but the highest sphere."

The demonstration was sparked by the plan of the Israeli government and the Israel Antiquities Authority to build on "ancient burial sites" in Jaffa and Ashkelon.

In London, the demonstrators claimed they were just "religious men… without political affiliation". They did, however, get their wish to be invisible. The Israeli Embassy had no comment on the event and an Embassy security guard seemed entirely unaware of it, asking "What protest?"