Paddington station: span 4 refurbishment and strengthening

London's Paddington station, the terminus of the Great Western Railway, was the masterpiece of the company's first chief engineer, Isambard Kingdom Brunel. The core of the station is a magnificent three-span arch roof on slender iron columns. However, in the early part of the twentieth century, the station was much extended, most notably by the addition of a grand fourth span to the roof structure. In recent times, span 4 has been neglected and is now undergoing refurbishment to restore it to its proper place as a grade 1 listed structure, alongside the remainder of the station buildings. The project will complete the renovation of the station's entire roof and complement the improved passenger information systems and retail developments. This paper first reprises the significant details of the original construction and looks in detail at the recent assessment of the span 4 roof and the associated parcel deck. Network Rail, the asset steward, is in the throes of undertaking the first major refurbishment of span 4 for over half a century and the paper describes the main aspects of the investigations and design that have led to the current works.