Welwyn Control, grey , metal, designed which must be operated (wound) by a signaller before he can clear a section signal when he cannot be given 'line clea' by the box in advance. The object uis to make the signaller stop and think what he is doing and was introduced after a serious accident at Welwyn Garden City in 1935. Located on model railway layout, gauge 1, Lancashire & Yorkshire Railway Signalling School, built 1912, by L&YR and Bassett-Lowke Ltd, with associated equipment.