Pembrokeshire has been called "the cottage garden of Wales", due to its good soil and the beneficial effects of the Gulf Stream, which provide a mild climate and a longer growing season than other parts of the country. The good climate and soil meant that the south of the peninsula was coveted by the Norsemen and Normans because it had "great plentie" of corn and cattle The county has prime agricultural land, much of which is located at about 70m above sea level, while to the north, the Preseli Hills rise to 500m above sea level and form uplands that are made up of heather and bracken, which are used for grazing sheep.Consequently, Pembrokeshire is classed as one of the most fertile counties in Wales, with its 392,300 agricultural acres having 14% of its land classed as of good quality, 67