GM trial survives - but 'war' goes on
The demonstrators gathered in a park beside the research centre, a good-natured throng sheltering from the scorching sun beneath a tree, enjoying spirited singing and delicious organic bread.
Speech after speech denounced GM as a tool of multinationals, a mechanism that would not benefit the poor, and science gone wrong.
Children played in the margins, people stretched out on the grass and the numbers slowly swelled. There are always arguments about turnout for these events: my colleagues and I reckon "about 200" is fair.
A short distance away, a group of pro-GM supporters clustered in another patch of shade. This was a counter-movement by the group Sense About Science. Appeals had gone out to show a pro-science presence. Again, trying to be fair, their number: about a dozen. Neither side exactly achieved mass-mobilisation.
One idea had been for the pro-science team to link hands to keep the antis at bay but the Rothamsted scientists had feared that might lead to trouble so the plan was dropped. Instead the group offered interviews to support the case for GM - and ice-creams, which were welcome on a sweltering day.
The big moment came when the speeches ended and the long-awaited march began. Linking arms and singing, the campaigners advanced towards the police line.
They were never going to get through. The leaders of the action, Take the Flour Back, had acknowledged that in advance. The security presence was too overwhelming.
The march reached the police and got no further. Any dreams of reaching the plot of GM wheat were dashed so the protestors sat down and chanted "No GM" instead.
One woman protestor had adorned herself with the word "biodiversity" in body paint. A young man with a banner started up a siren but a police officer pointed out that this would alarm the horses so he agreed not to use it. It was that kind of event - no scuffles, no violence.
And the GM trial survived. The security plan triumphed. At least for today. The challenge will be to maintain this level of protection in the weeks and months ahead.
One key test is which arguments gain ground with the public. It was consumer fears that led the supermarkets to declare themselves GM-free. Now the debate has moved on. Will the worries of the 90s continue now?
The scientists have learned to be as upfront and open as possible. That will make life harder for the campaigners.
Today marked a tactical victory for GM. But this is a war.