Most likely the coastguard blockhouse. These were built to help prevent smuggling. The Coastguard cottages were further up Hove Street, next door to the Ship.

Coastguard's cottage?

The 1932 OS map has the area of the present King Alfred defined as "Coastguard Station". The low buildings in the foreground are definitely the Coastguard Station, I imagine the house behind has some relation, perhaps the Coastguard's house.

Yes, an original building used by the coastguard, (likely built to deter smuggling), demolished in October 1969.

I have directories of Brighton and Hove and the 1917 edition of Pike's Blue Book has a map and designates this as Medina Esplanade with the battery clearly marked, however, there are no entries for Medina Esplanade in that directory. In the 1908-9 edition of Towner's Directory there are listings for Medina Esplanade but I am not sure they help. Next to the battery is Casa Amoena, Sutherland Duchess of; then St Aubyn's Residential Flats and other buildings are entered after these, going east. The building in question doesn't look like a Casa Amoena though - unless it was a mere shadow of its former self.

Further to my previous comment, I have been looking at photos in the James Gray collection, via the Regency Society website, and picture 108 in Volume 12 features this building and the text states the building was used by the coastguards. The photo was taken in 1968 and the buildings were demolished in 1969 - according to the text, which also says that the house was lived in until a few years before the date of the photos and it was demolished in October 1969. It still doesn't tell us whether it had a different use before that of the coastguards.

During the period that HMS Sussex RNR occupied the Battery complex the cottage was used by the duty shipkeeper who effectively was the caretaker/nightwatchman.

I am interested in the smuggling references. Does anyone have any infornmation they could share with me about smuggling in Hove?

This is just anecdotal but my close friend lived in St Leonard's Road, Hove, in the 1950's, until she was about 9. She was told there were tunnels and caverns, beneath their house, which linked to the beaches, and that they had been used by smugglers. I am not sure but there may be something to do with the area called Copperas Gap - I am sure there will someone on the mailing list who could help a lot more.

Casa Amoena had an amazing turret. Rather gothic and vertical in nature as a building. It was on the esplanade at the bottom of the St Aubyns South road between itself and St Aubyns Mansions. It was demolished to make way for the construction of the King Alfred in 1938.

Also interesting is that the RNR had the 'right to shoot' across the road and out to sea in an emergency.
Martin White...ERA White??

Out of interest, in the early 1960s I recall an RNR training establishment referred to as King Alfred. If I remember there was also the King Alfred Baths and a Ten Pin bowling alley there as well. Is this the same place, if yes does it still exist?