Yew Tree

I was walking round Saughton Park in Edinburgh this morning with a friend and we saw several of these ancient trees which we were able to identify fairly quickly as yew trees but wondered why they all had these growths around the trunk. I checked it out on the internet tonight and it gave this description which perhaps explains why some of the oldest trees in the whole of the UK are yew trees :-

'Once it has reached a certain size it can put out new shoots from the base of the trunk. As these develop they coalesce with the main trunk, appearing as ‘fluting’, or ridges around all or part of the trunk. Sometimes these become thick enough to support the tree in the form of ‘buttressing’. When the original trunk decays this ‘secondary’ growth forms the new tree.'