When did the Romans leave London?

The Greeks didn't own Egypt. After Alexander's death, his Macedonian general Ptolemy set up a kingdom there. The last of his line was Cleopatra who allied herself with Marc Antony against Octavian in the civil wars of the Roman Empire. After the his defeat of Antony-Cleopatra at Actium in 31 BCE, Octavian made Egypt a Roman province.