copies could not be made. 95% of the original drawings were found, with 1,100 scanned by 1993, and a further 140 in 2001. A few poor quality originals required re-drawing. Updated specifications were required to be drawn up to account for out-of-date material specifications and drawing notes whose original meaning could not be determined. Other design details were also obtained through interviews with Peppercorn's former assistant, J.F. Harrison. Changes from the original Peppercorn A1s Tornado design was modified where necessary to better suit modern manufacturing techniques and to fit in with the modern high-speed railway, while retaining the greater part of the original design. As an evolution of the Peppercorn Class A1, Tornado would also incorporate improvements that would have been made to the class had steam continued, such as correction of the rough riding faults. The following design changes were made for cost or operational reasons: An all-welded boiler (i.e. not riveted) Steel firebox (not copper) One-piece frames Roller bearings Improved front bogie Improved steam circuit Altered tender coal/water balance (more water) Overall weight reduction Additionally, to meet current safety and operation standards, Tornado includes: Up-rated electrical supplies Primary air (not steam) brakes LED cluster head/tail lamps Vacuum brakes (for heritage railway stock) 1 inch (25 mm) reduction in overall height (for overhead line equipment (OLE) regulations) Automatic Warning System (AWS) Train Protection & Warning System (TPWS) Data recorder European Rail Traffic Management System (ERTMS) compatible GSM-Railway (GSM-R) cab radio With advances in manufacturing, Tornado's long steel plates were electronically cut from one piece of steel, as opposed to the original Peppercorn A1s, which had two-piece frames riveted together. These are probably the most accurate steam locomotive frames ever produced. Despite their higher costs, roller bearings were used owing to the reliability they had demonstrated after a trial on some of the original engines. This caused an unforeseen problem in 2003 since the modifications made to the tender in the original fitting of roller bearings as an experiment to some Peppercorn A1s had not been properly drawn for the Cartazzi axle of the trailing wheels. A reduction in height from the original height was required by the Network Rail regulations, and was achieved by a redesign of the dome and safety valve mountings on the boiler, and by reprofiling of the cab roof and chimney. Testing was planned to occur with a lipped chimney, and on receipt of the