A further modification to the boiler design has been the use of hollow stays. The stays support and separate the outer boiler and inner firebox. The hollow stays act as an indicator of any cracks in the otherwise inaccessible stays, such cracks being revealed by water leaks. Leaks have in fact been detected and have led to the locomotive being unavailable for service. In July 2010 while replacement stays were fitted, Mark Allatt, chairman, The A1 Steam Locomotive Trust, commented "Although the problems with Tornado’s boiler are part of learning about the locomotive in today’s operational environment, they are a source of great disappointment to all of Tornado's supporters and customers and our customers' passengers. We are working as hard as we can to bring Tornado back to full health as soon as possible and back onto the main line where she belongs."