An application by Savills, on behalf of Bamburgh Castle Viewings Ltd, sought listed building consent for works carried out in 2014.
Northumberland Coast Area of Outstanding Natural Beauty (AONB) Partnership had expressed concern about light pollution.
In particular, concern was expressed about a fixing high above the West Ward.
Jessica Turner, AONB officer, said: “The justification is ‘providing illumination over the museum in response to overnight lead theft from the museum roof’.
"Whilst the Partnership acknowledges there is a balance between adequate security and lighting of a historic landmark, this fixing is at a considerable height from the much lower museum roof and illuminates an expanse of external wall high above the West Ward - as a result the primary purpose does not appear to be security or safety of movement within in the grounds at night.”
Savills explained that installation of the replacement LED lights was necessary to replace old, failing and inefficient fittings (500w sodium).
Its planning report states: ‘The replacement fittings present many improvements to the previous installation, both in the quality of the light omitted, method of fixing and visual impact of the light fittings, which are significantly smaller, simpler and more discrete.’
‘The overall effect of the lights to the keep is considered to provide an enhancement of the asset creating a dramatic night time effect consistent with the dramatic nature and setting of the castle.’
The council’s building conservation officer acknowledged the light fittings were ‘a small but detracting feature’ but accepted they could be justified to deter crime.
Planning officer James Hudson concluded: “The harm which may be caused is outweighed by the public benefit of crime prevention and the illumination of a very important heritage asset.
“While the proposals do have the potential to impact on the dark skies, suitably worded conditions restricting the use of the non-essential lighting to between the hours of dawn to dusk and strict positioning of the high lights to ensure that the light spill is not excessive, would limit the negative impact.”