Banners of "peace" and "love" were held high last night as Stop The War Coalition's rally drew in thousands to Parliament Square to protest against Syrian air strikes.
Leaders of the organisation spoke against Prime Minister David Cameron's view to pursue military intervention and chants of "Don't Bomb Syria, no more war" could be heard throughout the evening.
Demonstrators gathered to hear leaders of the organisation before marching to Tory Party Headquarters.
Protester Jacob Hannison said: "Why do we show that killing is wrong by killing civilians ourselves?
"It makes no sense."
Around 3000 people were listed on the STWC Facebook page as attending last night.
In a speech given by leaders of Stop The War Coalition, they said: "We don't expect MP's to show contempt for their leader, we expect them to vote against the war."
As protesters began to grow in number, Metropolitan police force members were seen to push them off the roads in order to keep Westminster streets clear.
Scotland Yard said one man was arrested for highway obstruction and being drunk and disorderly.
The decision, due to be made today following an all day debate in Parliament, will mean that the UK's air campaign in Syria will go ahead.
