Why can't you see Big Ben from Westminster Bridge in London?

I have never been in London , Colin, but I found this :
" You can’t actually see Big Ben. What you’re looking at is the clock tower, which is
called St Stephen’s. Big Ben is the bell inside that tower ".Source

Waiting for Colin, but that 'sounds' right.

It's a common misconception that the clock itself is called 'Big Ben'.The big bell that sounds the hours is 'Big Ben'.The nickname of the bell is that of Sir Benjamin Hall, the Chief Commissioner of Works when the new Houses of Parliament were being built.He was the man who had to answer to Parliament all through their cross-examinations over the delays, overspends, mistakes, mismanagements and so on( of which there were many). He was, therefore, a likely subject for Parliamentarian humour if anyone raised the subject of whether he deserved a memorial or reward. (An alternative suggestion is that it's from Ben Caunt, a corpulent ex-boxer who ran a pub about a mile away. As if Londoners would name a bell after a fat bloke who ran a pub )

And the tower is not St Stephen's but 'the Clock Tower'.

Another tricky question of this type is "Could Nelson see the sea from atop Nelson's column?" to which the unlikely answer is "Yes". That's because the River Thames is tidal for miles beyond Westminster and so technically part of the sea, being still seen as a tidal estuary. He could certainly see the Thames from his lofty viewpoint.