This is the Cleopatra's Needle on Embankment in London (the Victoria Embankment). It is near the Golden Jubilee Bridges (Hungerford Bridge / Hungerford Footbridges).
It was presented to Britain in 1819 by the ruler of Egypt and the Sultan Muhammad Ali in commemoration of the British victories on the Nile and at Alexandria. The British welcomed the gesture, but couldn't afford to move it at the time.
By 1877, the obelisk was still in Alexandria, when Sir William James Erasmus Wilson sponsered it at £10,000 to transport it to London.
After various problems getting it to London, it finally arrived and was installed on the Victoria Embankment by 1878.
It is flanked by two faux-Egyptian sphinxes, cast from bronze that have hieroglyphic inscriptions that say (in English) "the good god, Thuthmosis III given life". They seem to be looking at the obelisk / Needle rather than protecting it. That's due to the sphinxes improper or backward installation.