Ask a stockbroker what the biggest threat to the current rally is and he or she will probably respond with a one-word answer – tightening. In fact, an increasingly common fear among traders is that the end of ultra loose monetary policy, and the withdrawal of fiscal stimulus, could bring the whole market crashing down as it did in 1938.

Whether you subscribe to that view or something more benign, the moment of reckoning is drawing near. The rally, which started back in March and has seen the FTSE 100 rise 44 per cent, is about to face its biggest test.