see http://www.canterbury-cathedral.org/
In this image we see,first hand,one of the problems with low budget,digital cameras.Look closely and the tower appears to be leaning,slightly,to the right,whilst the repair work lift at this end,appears to be leaning to the left.It could just(just!!) be parallax,but more likely the effects of a low budget lens.My camera cost almost £500 when new,3 years ago,but the gubbins in it,ie electronic wizardry and that superb(for the money)all seeing 28 - 400mm (in 35mm terms)lens come at a price.See my shot of St.David's Cathedral in Pembrokeshire;inside,the columns DID lean,but the camera corrected the lean to a near perfect vertical.
see http://www.britishlistedbuildings.co.uk/en-170528-christchurch-cathedral-canterbury