Traces of older decorative schemes remain in the blue and white ‘Dutch’ tiles on the corridor wall and the door and hatch surrounds, and in the stone and marble slabs now resting on and around the settling tank; also in the damaged wall-plaque, identifying the bath as ‘nearly 2000 years old’ and a relic of the days of ‘Titus or Vespasian’.The source of the water coming into the Bath has never been properly established, and may have varied over time.

When tested in 1981, samples were found to have ‘the basic characteristics of ground water, but containing high levels of nitrate and phosphate.’[3][4] In 1609–1613 James I had the first version of the old Somerset House lavishly enlarged and refurbished for his queen, Anne of Denmark.

[1][3] The refurbishment included the reorganization of the gardens and the building of an immense grotto-fountain showing the Muses and Pegasus on Mount Helicon, designed by the brilliant French engineer, Salomon de Caus.

[5][6] Contemporary documents establish that the cistern supplying this fountain was ‘over the Strand Lane’ and was fed by pump from the grounds of Somerset House.

The redevelopment of the remains of the derelict cistern structure as a cold bath seems to have been the work of a Mr James Smith, who moved into No 33 Surrey Street in the mid-1770s.

33, Surry-street, in the Strand … for the Reception of Ladies and Gentlemen, supplied with Water from a Spring, which continually runs through it.’[11] Two years later he enlarged his offering by adding a second, freshly constructed bath next to the first, lined with marble and surrounded by a stone-flagged floor and tiled walls.

At any rate, it is in 1838, without any prior warning, that the establishment suddenly appears in a trade directory as the ‘Old Roman Spring Baths’, under the proprietorship of a Mr Charles Scott.

At the same time, Glave refurbished the older basin for bathing by transferring the stone flooring, marble lining and wall tiles to it from its now decommissioned neighbour, along with some new partitioning, changing-stalls and decorative sculpture.

The Bath was bought, for £500, by the Rector of St Clement Danes, the Reverend William Pennington Bickford, who, along with his allies the journalist and historical writer Edward Foord and the graphic artist Fortunino Matania, was the last of the great believers in its Roman origins.

[25][26] Aiming to get back to the ‘real’ Roman fabric, he had all of the Glave décor apart from the tiling stripped off (some of it is still there on top of the settling tank), and dreamed of restoring the Bath to its original magnificence – ironically, by once again covering it in marble and stucco, this time of the ‘right’ kind.

[27][28] Pennington Bickford's ambition was for the Bath to become one of London's most attractive historic monuments, and to bring both cultural cachet and much needed funds to St Clement Danes and its parish.

Edward Foord, for his part, produced a series of pamphlets and newspaper articles arguing confidently for the Bath's Roman credentials and offering speculative reconstructions of its history, layout and workings.

[29] Pennington Bickford's plans came to nothing for want of funds, and when he and his wife died in 1941, the Bath was bequeathed to the patron of St Clement Danes, William Cecil, 5th Marquess of Exeter, along with what they hoped would be the means of securing its preservation as a historic monument.

The London County Council agreed to see to the maintenance, and the money was provided by another of the Bath's fans, the timber magnate Montague L. Meyer.

Collins took evidence from a wide range of sources, including a surviving daughter of the last proprietor before Henry Glave, the now elderly and cantankerous historical writer Edward Foord,[31] and most significantly of all a penetrating analysis of the Roman story compiled in 1906 by an anonymous predecessor at the LCC.

A recent project sponsored by the Cultural Institute at King's has indicated some interesting ways in which digital resources could be used to explore the Bath's history and make it accessible to virtual visitors, but lacks further funding.