To one side of the main entrance, the police had gone to the effort of establishing a 'pig-pen' for everyone, and most of those who had already arrived had entered it. When the Leeds/Bradford contingent turned the corner into the entrance of the site, they headed straight past the pen, with several asylum seekers carrying their banners ahead. The effect was the establishment of a blockade on the driveway, though this was hardly a problem, with almost no travel on or off site throughout. A single expensive black car was allowed off site and then back on again by the police, who resorted to shoving tactics to make way for it. This required some manhandling of Samba players, on of them being given no less than 5 'final warnings' that they'd be arrested if they didn't move (a vicar also received one such warning).
After the band died down, various people took the megaphone and gave speeches, some of them former residents of Harmondsworth or Colnbrook, some are running current campaigns to remain (either for themselves or others). Someone talked about an upcoming Trade Union conference, and the local MP spoke about his work with asylum seekers. This would have been better had it not been John McDonnell MP, the old-leftist contender for the Labour leadership, who's footsoldiers dutifully moved through the crowd handing out the now-familiar "John 4 Leader" materials.
At around 1:30, allowing a clear hour before visiting time would begin (apparently we can't have protesters being visitors, as they're a security threat) the band began playing again. They began to make their way out onto the dual carriageway (not a motorway as stated by some) in the direction of their coaches. Most of the crowd followed, some on the road and others on the pavement. The police made a few small attempts to clear the road but this failed.
Once the march had proceeded a few hundred meters, a couple of police officers decided to take things into their hands, and started forcing people out of the road. At this point a couple of people carriers, minimally marked as belonging to the met, tried to drive through the protest, and a handful of cops took to wrestling protesters out of the way. Several protesters managed to get 'cleared' several times. A male protester on a bike was thrown off onto the verge, and one of the band's conductors was particularly assaulted by the police.
At this point 4 van loads of police arrived from the other direction and a large group of police got out and began lining up. When the marchers reached the junction where they needed to turn, the police acted as though they expected the march to continue on. While marching onto the M4 would have been a wonderful way to get killed, this wasn't on the minds of the protesters, who were far more concerned with finding their coaches. The police proceeded to march either side of the crowd along the final road towards their buses. No arrests, but some fairly close calls.
There was widespread concern that asylum seekers were being put at risk during the march, but in practice, most of these seemed to be thankful to the protesters who had stuck it out in the middle of the road.