I don't think the protests were useless even if they didn't stop the war. It allowed the anti war opinion to solidify, particularly when there were no WMDs found (surprise).
Tony Blair is now widely reviled in the UK, and you can hardly find anyone who will admit to have supported the war.
Fair enough. It was certainly a learning point for me, personally. And it was probably an on-ramp into understanding imperial and neo-liberal politics that set a lot of folks of my generation into Occupy.
At the same time, I wish that protesting felt effective; the stated goals weren't achieved, and that is a fact. I've never been satisfied with being "right" about these horrors, even if I've been "right" a lot in my life.
And protesting is way more fun and less risky than the direct actions that seem to be for more effective in having measurable effects on efforts around ICE.
Tony Blair is now widely reviled in the UK, and you can hardly find anyone who will admit to have supported the war.