Sailors long feared Grenen, as many ships have run aground on the shallow reef through history. The first light signals were erected in 1561 on orders from King Frederik II after international pressure. It was not very effective and was not regularly attended, so from 1627 Skagen's Vippefyr, a coal- and wood-fired tipping lantern, replaced it until 1747, when Skagen's White Lighthouse was built. The 44-metre high Skagen's Grey Lighthouse has done the job since 1858, and in 1956 the 26-metre tall Skagen's West Lighthouse was added, making the heavy traffic in and out of Kattegat adequately safe.[citation needed]