The railway network in Great Britain consists of approximately 10,000 miles of track and serves around 2,500 stations. The railway infrastructure is owned and operated by Network Rail while passenger services and all but 17 stations are operated by a total of 26 privately owned train operating companies (Network Rail directly operate the remaining 17 principal stations). The Irish network is naturally much smaller, with just 300 miles of track in Northern Ireland and around 1,400 miles of track in the Republic of Ireland, less than half of the original total of 3,600 miles of track. There are also 1,200 miles of private 36 gauge narrow gauge railways used for transporting peat by Bord na Móna, a company of the Irish government.
In 2005/2006 there were over 1 billion passenger journeys in Great Britain, the largest number since 1959, and during 2005/6 Network Rail will have spent approximately £5.1 billion on the routine maintenance and upgrading of the network. Network Rail continues to spend the equivalent of £14 million every day on maintenance and upgrading of the network.
In Ireland, the rail network has arguably suffered from much more serious under-investment than its mainland counterpart and passenger numbers are often negligible on some routes, however the two railway companies on the island have recently spent considerable sums upgrading track and rolling stock.
Incorporating a number of new developments in British steam locomotive technology, the design of the Packets was among the first to use welding in the construction process; this enabled easier fabrication of components during the austerity of the war and post-war economies. The locomotives featured thermic syphons and Bulleid's controversial, innovative chain-driven valve gear. The class members were named after the Merchant Navy shipping lines involved in the Battle of the Atlantic, and latterly those which used Southampton Docks, an astute publicity masterstroke by the Southern Railway, which operated Southampton Docks during the period.