The only thing stopping the NRM from building a new boiler for 850 is the NRM itself with it's ether lack of funding or unwillingness to have something new that's as big as the boiler. In my mind a new one should be built to replace what even to a casual observer like my self is a knackered, patched and repatched boiler. But then it is all to simple for me to say that one should be built when a new boiler now a days coasts between 100,000 to 400,000 pounds to build what is a huge chunk of funding that could be used on other engines. Don't get me wrong i like Lord Nelson but there has to be a limit to the amount of engines the NRM has running on the mainline or out and about. Next year Cromwell will be back in all it's glory and hopefully if nothing else goes wrong we should have the Flying Scotsman in the near future. Not to mention we have everyone's favourite GWR 4-4-0 City of Truro doing the rounds and Sir Lamiel now back after boiler problems. Add that to the already growing number of mainline engines that will be up and running next year, hopefully. These include the new build Tornado and the two Royal scots which should be ready next year as well as a castle and hopefully a single chimney king to join the other that is already out there, or at least will be next year. And this is not even counting the three A4's that will be on the mainline or any of the Bulleids that might make a appearance or two.