yet, but a very worrying new detail. the source also telling me that this was a crude device, a poorly made device as well. and, of course, it didn't go off. and if this was tapt, that needs to be confirmed, but if it was tapt, if it had gone off you could have seen dozens of casualties, perhaps very few people getting out of that train carriage alive. it's a high explosive. many times more powerful than the boston devices were. >> one thing we know we've had to learn about tatp it's very unstable and the fact that it's crude but involves tapt points you where. >> the fact it's poorly made could indicate this was somebody who had no training, they were trying to do it off the internet. it's possible that the person who did this could have got training overseas and just didn't do it, particularly well. you're right, tatp what is they