George Catt's widow Emily sold the Tidemill to the Newhaven Harbour Company in 1879 who in leased to other members of the Catt family but by 1883 the mill closed. The mill house and cottages continued to be occupied by the families of the former mill workers, harbour employees farmhands and holiday makers. The Mill Building was used as a bonded warehouse until it was demolished in 1901. However this was not the end of the industrial uses of the site.
In 1904 the Marconi Radio Company set up a wireless station on the beach. The station was used to report on the arrivals and departures of the cross channel shipping and by 1912 ship to shore communications facilities had been established.
The first world war saw the construction of a seaplane base, complete with a hanger for seaplanes, covering the area of two football pitches. The seaplanes were deployed against German U boats in the English Channel. The Royal Naval Air Station, Newhaven had opened at Tidemills in May 1917. The air station continued to expand, a second hanger was built and at least 6 aircraft were flying daily. The RAF formed in April 1918 took over the site from the RNAS but after the cessation of hostilities the station closed and the steel hangers dismantled
After the end of the first world war, Tidemills began to grow as a holiday village using converted railway carriages left over from the air station. In 1922 parts of the old mill became a convalescent home for injured race horses. The horses were bathed in salt water and galloped along the foreshore. The facility continued to operate until the start of the second world war in 1939. In 1924 part of the old seaplane station site saw the creation of the Chailey Heritage Marine Hospital for Boys. Founded by the Chailey Heritage School, the marine hospital was an extension of the main hospital at Chailey. Although the hospital was acclaimed as in glowing terms, the outbreak of the second world war resulted in Tidemills being evacuated as it was thought it would be used as a possible invasion site. For a while it was used by the Army as a training area. Later buildings were demolished so they would not provide cover for invading forces.
The concrete apron to the west of Newhaven had another, if temporary, use in 1970/71 as the construction site for the Royal Sovereign Lighthouse, still in operation off Eastbourne.
More information about Tidemills can be found in the Seaford Museum publication "Tidemills - A village ahead of its time" available from the Martello Tower, Seaford.
Moving further inland will bring you to Bishopstone Halt