A 75-foot banner was unfurled along Westminster Bridge this morning, as outrage grew over the Israeli bombing of a UN school in Gaza.
At least 17 people were killed and 90 wounded in the shelling of the Jabalia Elementary Girls School early on Wednesday, but instead of slowing the pace of the military offensive it appears to have encouraged it, with prime minister Benjamin Netanyahu calling up another 16,000 Israeli army reservists.
The banner read: "UK: Stop arming Israel" and was put up in the middle of rush hour, as commuters looked on.
"We demand our government stops selling arms to Israel, a country which is horrifically killing and injuring thousands of men, women and children in Gaza," a London Palestine Action activist said.
"As MPs go off on their summer holidays we've come to remind them that our government has blood on its hands.
"Our leaders are calling for sanctions and an arms embargo on Russian but we are continuing to arm Israel.
"We are complicit in this slaughter. It's got to stop now."
Britain has about £10 million riding on Israeli military contracts, compared to just £5,539 for the Palestinian territories.
It supplies the Israeli Defence Force with components which are used in sniper rifles and small arms, as well as parts for F-16 combat aircraft and Apache helicopters.
Amnesty International, six Nobel Peace Prize laureates and over 90 celebrities have called for an immediate arms embargo on the country.
The United Nations is calling for an immediate investigation in to alleged war crimes after a series of Israeli bombing attacks on hospitals, ambulances and schools.
Its Relief and Works Agency (UNRWA) spokesman, Chris Gunness, broke down in tears during a TV interview yesterday as he described what was happening in Gaza.
He later told Buzzfeed the division was at "breaking point" in the face of the humanitarian catastrophe.
"My feelings pale into insignificance compared to the enormity of the tragedy confronting each and every other person in Gaza at this time," he added.
"It’s important to humanise the statistics and to realise that there is a human being with a heart and soul behind each statistic and that the humanity that lies behind these statistics should never be forgotten."
The death currently stands at 1,363 Palestinians. One Palestinian child has died every hour since the Israeli operation began.
Gunness said the school, which was holding 3,000 people who had followed Israeli orders and fled their home, had told the army its precise location 17 times.
"Children were killed as they slept next to their parents on the floor of a classroom in a UN designated shelter in Gaza," UNRWA commissioner-general Pierre Krahenbuhl said.
"Children killed in their sleep; this is an affront to us all, source of universal shame. Today the world stands disgraced."
The Israeli military said it was investigating the attack, but many observers have lost faith in its assessments since it insisted only an empty shell was fired at the previous UN school which came under attack.
UN testimonies said numerous shells fell within the vicinity of the school and journalists on the scene reported debris consistent with mortar rounds.
Fifteen people died and 200 were injured during the strike.