The first geometric, self-supporting spiral staircase in Britain is in the Queen's House, Greenwich. It is 'geometric' because each step supports the stair above: there is no central column. Andrea Palladio, father of the Palladian style of architecture, had described and praised such staircases, 'void in the middle'.
Inigo Jones studied Palladio's work and followed his example in the Queen's House. Nicholas Stone, his mason, introduced a crucial innovation. Rather than relying only on the overlap between steps for support, he also introduced a rebate: a groove along the bottom of the riser, also known as an 'interlock'.
Stamp Office staircase, Somerset House
The difference is neatly illustrated in the Stamp Office staircase at Somerset House. The lower level, with its short flights and narrow steps, did not need rebates: we can see that the steps simply rest on top of each other. The much fancier upper level, though, is rebated: you can see that each step is slotted into the one above, rather than simply sat on the one below. (As usual, you can click the picture to enlarge it.)
Stone's innovation allowed such staircases to be built more dramatically, yet remain structurally sound. Geometric staircases proliferated in the eighteenth century, falling out of fashion only with the Gothic revival in the nineteenth.
Why was Britain's original named the Tulip Stairs, though? It's apparently a reference to the stylised flowers in the balustrade - although these are thought to be fleurs-de-lys, not tulips at all. They were the family emblem of Queen Henrietta Marie, wife of Charles I, for whom the house was built. (In fact, when work began, it was for James I's wife Anne of Denmark - but she died during building; when work resumed, it was for Henrietta Marie.)
After the Civil War, the Palace of Greenwich in front of the house was demolished, giving it a view across to the Thames. When a new Hospital for Seamen was established on the palace site, Queen Mary II famously insisted that the river view must remain. Thus Sir Christopher Wren designed two pairs of courts, creating the riverside vista we are now familiar with - and leaving the Queen's House view unimpaired.
It is now part of the National Maritime Museum, housing its art collection. Visits are free, and worthwhile for the displays - but don't forget to look at (and climb) this fabulous staircase.
St Paul's Cathedral: Geometric Staircase
London has another famous seventeenth-century example: the Geometric Staircase of St Paul's Cathedral. A three-hundred-year-old masterpiece, which has starred in Harry Potter, it can be seen on the cathedral's Triforium Tour.