The opening of the Great Western Railway in 1841 removed much of the canal's traffic, even though the canal company lowered tariffs.
 In 1852 the railway company took over the canal's operation, levying high tolls at every toll point and reducing the amount spent on maintenance.
Ice-breaking was stopped in 1857, and traders were further encouraged by preferential tolls to use the railway rather than the canal.
In 1861 a new order prohibited any traffic on the canal at night, and, in 1865, boats were forced to pass through locks in pairs to reduce water loss.
By 1868 the annual tonnage had fallen from 360,610 in 1848 to 210,567.
In the 1870s water abstraction from the canal near Fobney Lock followed the regulations introduced in the Reading Local Board Waterworks, Sewerage, Drainage and Improvements Act of 1870, and contributed to the silting up of locks and stretches of the canal.
 Several wharves and stretches of towpath were closed.
In 1877 the canal recorded a deficit of £1,920 and never subsequently made any profit.

The Somerset Coal Canal and Wilts & Berks Canal, which each supplied some of the trade from the Somerset Coalfield to the Kennet and Avon, closed in 1904 and 1906 respectively.
In 1926, following a loss of £18,041 the previous year, the Great Western Railway sought to close the canal by obtaining a Ministry of Transport Order, but the move was resisted and the company charged with improving its maintenance of the canal.
Cargo trade continued to decline, but a few pleasure boats started to use the canal.

During the Second World War a large number of concrete pillboxes were built as part of the GHQ Line - Blue to defend against an expected German invasion; many of these are still visible along the banks of the canal.
They were generally built close to road and rail bridges, which would have formed important crossing points for enemy troops and vehicles.
After the war the Transport Act of 1947 transferred control of the canal to the British Transport Commission, but by the 1950s large sections of the canal had been closed because of poor lock maintenance following a breach in the bank west of the Avoncliff Aqueduct.
The last through passage was made in 1951 by nb Queen.
The opening of the Great Western Railway in 1841 removed much of the canal's traffic, even though the canal company lowered tariffs.  In 1852 the railway company took over the canal's operation, levying high tolls at every toll point and reducing the amount spent on maintenance. Ice-breaking was stopped in 1857, and traders were further encouraged by preferential tolls to use the railway rather than the canal. In 1861 a new order prohibited any traffic on the canal at night, and, in 1865, boats were forced to pass through locks in pairs to reduce water loss. By 1868 the annual tonnage had fallen from 360,610 in 1848 to 210,567. In the 1870s water abstraction from the canal near Fobney Lock followed the regulations introduced in the Reading Local Board Waterworks, Sewerage, Drainage and Improvements Act of 1870, and contributed to the silting up of locks and stretches of the canal.  Several wharves and stretches of towpath were closed. In 1877 the canal recorded a deficit of £1,920 and never subsequently made any profit.
The Somerset Coal Canal and Wilts & Berks Canal, which each supplied some of the trade from the Somerset Coalfield to the Kennet and Avon, closed in 1904 and 1906 respectively. In 1926, following a loss of £18,041 the previous year, the Great Western Railway sought to close the canal by obtaining a Ministry of Transport Order, but the move was resisted and the company charged with improving its maintenance of the canal. Cargo trade continued to decline, but a few pleasure boats started to use the canal.
During the Second World War a large number of concrete pillboxes were built as part of the GHQ Line - Blue to defend against an expected German invasion; many of these are still visible along the banks of the canal. They were generally built close to road and rail bridges, which would have formed important crossing points for enemy troops and vehicles. After the war the Transport Act of 1947 transferred control of the canal to the British Transport Commission, but by the 1950s large sections of the canal had been closed because of poor lock maintenance following a breach in the bank west of the Avoncliff Aqueduct. The last through passage was made in 1951 by nb Queen.
Kennet and Avon Canal