Portland Old Low Lighthouse is located at the bottom of Branscombe Hill at Portland Bill. Both the Old Low and High Lighthouses were established in 1716. When lined up with the Old Higher Light, they formed a transit line, marking the offshore Shambles sandbank. The Old Lower Lighthouse is taller than its counterpart, and both lighthouses are sometimes confused.
Both lighthouses were installed with enclosed lanterns and coal fires. They were leased to a private consortium. However, they were both poorly maintained and shipowners complained about their efficiency. Following the expiry of the lease in 1777, Trinity House took over the lease and maintenance of the lights.
In 1788, the High and Low Lighthouses were rebuilt, and the Low Light was demolished the following year.
The Low Light was later modernised again in 1856 under the supervision of James Walker. The dwellings were demolished, and new quarters were built for the keepers. Both Low and High lights were fitted with new optics and more efficient oil lamps. The High Light was also increased in height by 15 feet.
Trinity House decided to rebuild both towers in 1866, and James Douglass designed these on the recommendations of James Walker. The Low Light was five storeys and around 85 feet high, and the High Light was a two-storey building 50 feet high. Both lighthouses had a first-order fixed dioptric Chance optic with a five-wick oil lamp.
Following the re-establishment of the High Light in March 1867, the Low Light came into operation in October of the same year.
In 1901 fifteen ships were wrecked, and Trinity House decided that the two lights were no longer suitable. The new Portland Bill Lighthouse was built and replaced the High and Low Lights in 1906. The two redundant lights were put up for auction in 1907. However, the Low Light initially failed to reach the reserve and was withdrawn from sale. It was later sold privately and used as a summer retreat.
The lighthouse was later turned into the Longstone Ope Tea Rooms and Gardens. By the mid-1930s, it had been established as the Lower Lighthouse Guest House and Restaurant, run by Mrs Broomhead. It was also known as Bay View.
Following the Second World War, the Lighthouse was abandoned and left derelict.
In 1951 ornithologist Dr Ken Rooke was studying bird migration in the area. Many of the visiting ornithologists were staying in temporary accommodation. The lighthouse was sold by Helen Brotherton, who restored it and converted it in 1961 into a bird observatory. Sir Peter Scott officially opened it in March 1961.
The lighthouse and adjoining cottage provide hostel accommodation as well as a bird observatory.