Analysis of information sources in references of the Wikipedia article "Grizel Niven" in English language version.
Part of the reason that the young Niven enjoyed his school holidays in Bembridge so much is that his mother saw very clearly that her two teenage sons needed space and freedom to let their hair down — so much so, in fact, that she built an extension to the rear of the house which was quickly dubbed the 'Sin Wing'. [When] David and his brother used to come in rather noisily at night [...] his mother got a bit cross so she built two bedrooms and a bathroom at the back.