Morris was particularly concerned about the practice, which he described as 'forgery', of attempting to return functioning buildings to an idealised state from the distant past, which often involved the removal of elements added in their later development, and which Morris saw as contributing to their interest as documents of the past. Instead, he proposed that ancient buildings should be repaired, not restored, so that their entire history would be protected as cultural heritage. Today, these principles are widely accepted.
Today, the SPAB still operates according to Morris's original manifesto. It campaigns, advises, runs training programmes and courses, conducts research and publishes information. As one of the National Amenity Societies, the Society is a statutory consultee on alterations to listed buildings, and by law must be notified of any application in England and Wales to demolish in whole or part any listed building. It currently has c. 8,500 members (2012). The Society also has a branch in Scotland.
The society's Mills Section is the only British national body concerned with the protection, repair and continued use of traditional windmills and watermills; Ken Major carried out much work on its behalf.
For its dedicated service to heritage, the society was awarded the European Union Prize for Cultural Heritage / Europa Nostra Award in 2012.