Slippery Jack (Suillus luteus)
At first sight this might appear to be a waxcap fungus bit on closer inspection you will quickly see the classic yellow sponge underside to the cap and so change the thoughts to the range of potential boletes species. The shiney surface gives this one the common name of Slippery Jack. As with many of the Suillus species (still boletes family) these are associated with acidic soils and pine, usually Scots Pine. Usually solitary, sometimes in a small group Slippery Jack appears in the autumn.
Edible but sometimes purgative so be warned.
Find out more about Slippery Jack in Dorset here: www.natureofdorset.co.uk/species_panel/Slippery%20Jack?vd..