The Shambles sandbank is marked by a red sector light. Portland Bill and Chesil Beach are the graveyards of many vessels that failed to reach Weymouth or Portland Roads. The Portland Race is caused by the meeting of the tides between the Bill and the Shambles sandbank about 3 miles SE. Strong currents break the sea so fiercely that from the shore a continuous disturbance can be seen.
As early as 1669 Sir John Clayton was granted a patent to erect a lighthouse, but his scheme fell through and it was not until early in the eighteenth century that Captain William Holman, supported by the shipowners and Corporation of Weymouth, put a petition to Trinity House for the building of a lighthouse at Portland Bill. Trinity House opposed it suggesting that lights at this point were needless and shipowners could not bear the burden of their upkeep. The people of Weymouth continued their petition and on 26 May 1716 Trinity House obtained a patent from George I. They in turn issued a lease for 61 years to a private consortium who built two lighthouses with enclosed lanterns and coal fires. The lights were badly kept, sometimes not lit at all, and in 1752 an inspection was made by two members of the Board of Trinity House who approached by sea to find "it was nigh two hours after sunset before any light appeared in either of the lighthouses". With the termination of the lease the lights reverted to Trinity House. In 1789 William Johns, a builder of Weymouth under contract to Trinity House, took down one of the towers and erected a new one.It was sited so that it served as a mark by day or night to direct ships moving up and down Channel or into Portland Roads clear of the Race and Shambles.
In August 1788 Argand lamps were installed, Portland being the first lighthouse in England to be fitted with them. In the upper or old house there were two rows, seven in each row, lighted with oil and furnished with highly-polished reflectors. Low light tests were made by Thomas Rogers with his new lens light, and six Argand lamps were installed, their lights increased by lenses.
A seven metre tall white stone obelisk was built in 1844 at the Southern tip of Portland Bill as a warning of a low shelf of rock extending 30 metres south into the sea, which still stands near the current lighthouse.
New high and low lighthouses were built in 1869, but in 1906 Trinity House replaced them with a single tower: the present lighthouse. The old towers can still be seen from the outside - the low light, which is now a bird observatory and field centre, has retained its original appearance but the high light lantern has been removed.
The present optic at Portland Bill is very unusual as due to the arrangement of the panels the character gradually changes from one flash to four flashes between the bearings 221°and 244° and from four flashes to one flash between bearings 117° and 141°.Portland Bill Lighthouse was automated on 18 March 1996. The lighthouse is now monitored and controlled from Trinity House’s Planning Centre in Harwich, Essex.