Referring to an incident on Friday (September 1), RMT general secretary Mick Cash said three pickets were approached by Southern security guards, British Transport Police (BTP) officers and a manager for Southern within ten minutes. But a spokesperson for Southern said: "Quite simply, the RMT have repeatedly placed their picket line within station property, and they have been politely asked to move on repeated occasions which they have refused to do." A letter from Mr Cash to Southern bosses said: “I was shocked to find that at 4am this morning three RMT pickets at Brighton were approached by three BTP officers, three Southern security guards and ten minutes later a Southern manager - seven people intimidating three pickets. "They started by stating my members should leave as they were on private property. It was pointed out that even by your own admission the property is owned by Network Rail, not Southern, and Network Rail has not asked the pickets to leave. It was suggested that the pickets stand outside the adjacent hotel. Perhaps you can explain why our pickets should picket a hotel – and presumably be on their private property. "Your manager accused my members of being on an illegal picket and when the paperwork was shown to him and the BTP officers, showing clearly that one of the pickets was the nominated picket supervisor, they stated that as the paperwork was produced by the union itself it wasn’t legal. This is absolutely wrong and you should advise you managers that they should be aware of the legal requirements and not try and make up the rules to suit themselves and their augments. The pickets had also registered with the Sussex Police and yet again this was questioned. "To add to the intimidation your manager informed my picket supervisor that he was filming the discussion on a bodycam. However, despite best practice he only decided to do so halfway through the intimidation. He also harassed my members by continuously asking if they were going to leave the premises even to the point where he said ‘for the fourth time are you leaving’. He had been advised that the pickets were not leaving as they felt they had a legal right to be there, it is bullying to keep asking the same question when you know you are going to get the same answer. "Can I say that over the years we have picketed on many occasions and in many locations as is our legal right – albeit a more and more difficult one. There have been very few instances of problems and most companies, whilst obviously not being happy, respect our right to do so and do not act in the way your company has on this occasion. To send seven people to try and intimidate a legal picket is unacceptable and I am seeking your assurance that this will cease immediately.” The RMT union, which represents conductors, has been locked in a year-long dispute over driver-only operation with Govia Thameslink (GTR), the company operating the Southern franchise. Union members were on strike on Friday (September 1), and continue industrial action today (September 4) for 24 hours.