the column and a fissure extending half its length—was still visible a decade later. In 1951 the Sunderland Echo reported that children had unsealed the door to the staircase and climbed the monument to search for pigeons' eggs; the National Trust employed a local builder to reseal it. In 1959 the National Coal Board repaired the monument after it was damaged by subsistence caused by mining: its northern, western and southern sides had become cracked, and part of the walkway had detached and overhung the interior. Stone blocks were replaced with concrete slabs with stone facings. Because of further settlement, Penshaw Monument was underpinned in 1978. The next year the western side was taken apart, and damaged lintels were replaced with ones made of reinforced concrete; the new lintels have buff-coloured artificial stone facings. 1980s to 2000s: floodlighting and further repair In 1982 a grant from the Countryside Commission allowed the National Trust to purchase of land surrounding the monument, including much of the south-facing side of Penshaw Hill and the woodland to the north-west. The monument has been illuminated at night by floodlights since 1988, when Sunderland City Council paid £50,000 () for them. Between 1994 and 1996, several of these lights were stolen; Northumbria Police said they may have been used as grow lights for the cultivation of cannabis. In 1994, The Journal reported that Penshaw Monument "might be sinking" after two surveys showed the levels of the bottoms of the columns were not even. The National Trust hired the civil engineer Professor John Knapton to carry out a third, more comprehensive survey of the monument to assess whether movement had occurred. In 1996 the National Trust said it was spending over £100,000 () to restore the monument. Its columns and lintels had deteriorated and were repaired. Its cast iron cramps had rusted, causing them to expand and stress the monument's stonework—these were replaced with stainless steel cramps bedded in lead. Repointing was done using lime mortar made from lime quarried at the National Trust's pits on the Wallington estate in Northumberland. However, the surface of the stone, which has been blackened by soot, was not cleaned so that it would remain "a reminder of the area's tradition of heavy industry". The Trust later said: "Now that mining has ceased, the blackness seems particularly evocative and proposals for cleaning have been resisted". On 16 November 2005 a group