10:01pm UK, Friday September 24, 2010 SKY NEWS The threat level to Great Britain from Irish-related terrorism has gone from moderate to substantial, meaning an attack is a "strong possibility", the Home Secretary has said.  Published for the first time, the threat assessment is "to encourage people to be alert to the increased threat from Irish-related terrorism", the Home Office said. More.. Overall, the threat is still lower than the threat level to the UK from international terrorism, which remains at severe, meaning an attack is highly likely, according to the Joint Terrorism Analysis Centre (Jtac). There had been fears of a targeted attack on the Tory conference, reminiscent of the Brighton bombings in the 1980s. Yet, speaking ahead of the Labour Party conference in Manchester this weekend, Sky’s political editor Adam Boulton said: "It's clear that there doesn't appear to be a specific threat to party conferences this year." Boulton went on: "Obviously they are seen very much as a potential target, and everyone who has to go to them still has to put up with a great deal of security and searches." He added: "It's not a specific threat to party conferences, it's simply that they have raised the level of threat, which suggests that they have credible intelligence." The head of MI5 warned last week that dissident Irish republicans could attempt to mount a new wave of terrorist attacks on the British mainland. Jonathan Evans, the director-general of the Security Service, said there has been a "persistent rise" in "activity and ambition" by dissident groups in Northern Ireland over the past three years. While they did not have the capacity to return to the levels of violence caused by the Provisional IRA at the height of the troubles, he said they still represented "a real and rising security challenge". His warning came after one group, the Real IRA, publicly threatened to target banks and other financial institutions in the City of London, a...