It's been a long road. Yesterday evening, in a victory for free speech, the Director of the London School of Economics apologised for intimidation of the university's Atheist, Secularist and Humanist Society at their Freshers Fair. Promoting their society at the October fair, the society's President and Secretary, Abhishek Phadnis and Chris Moos, were surrounded by eight security guards, at the request of the students union, for refusing to remove t-shirts showing the popular cartoon Jesus and Mo. When they eventually did put on jumpers, the were assigned a guard each to follow them for the rest of the day.

As President of the National Federation of Atheist, Humanist and Secular Student Societies I've written on this website before about the challenges many of our members face when legitimate criticism of religion is slammed and shut down as "offensive" or even "racist". Yesterday's statement represents an important step forward in the fight for free expression on UK campuses for our member societies. Its significance will be felt beyond the LSE by universities and students unions across the country who resort too quickly to censorship in the face of religious sensitivities. To truly understand the significance of yesterday's statement requires an understanding of just why it happened.

The decision of the LSE's Director to review events on the day, going against the actions of his staff and students union, was a very mature and doubtless politically difficult one that should be applauded but it didn't take place in a vacuum. The apology followed over two months of press coverage, public outcry and legal pressure. The press coverage was unanimously against the LSE's attempted censorship with comment pieces in every broadsheet. This was important, as part of the reasoning behind the intimidation was concern about potential outcry from religious students – atheists have shown that we will make a fuss too. A university concerned about its reputation will take note of that.

But I believe our most powerful and effective argument wasn't reputational but legal. We are indebted to pro bono legal advice from David Wolfe QC, who helped the LSE ASH in drawing up their formal complaint, with input from no less than 3 professors of law. The 15-page document sets out in no uncertain terms the legal responsibilities of universities to ensure the freedom of expression of their students and to what extent this freedom can and cannot be curtailed. It took weeks to draft and makes very clear that the LSE got its decision wrong. We also made clear that we would, if necessary, take the matter to court. It was very likely this pressure that secured yesterday's apology, after 6 weeks of consideration by the School.

The impact of this has already been felt elsewhere. I attended a meeting last week at another London university, where the students union had told its Atheist Society that they couldn't criticise Christianity in their posters, using a bizarre interpretation of the Equality Act as their justification. The society stuck to their guns and, bolstered by the legal assurance already secured at LSE, argued the case that their free expression was being curtailed. The union backed down.

Universities will have paid close attention to the LSE's behaviour. It is clear that the case for free speech has been made and won. While not quite a judge's ruling, a more subtle precedent has been set: freedom of expression does not bow to religious sensitivities. Well done to Chris and Abhishek for sticking to their principles and taking this to the end. Here's hoping no more students have to.