Wandering About in London

Having a day off and having arranged to meet Ms T and friends I headed into London a little early and turned myself into a tourist. I tried to do some of the things they do. I walked up from Victoria, a bit hungry, and had a rather unpleasant club sandwich at a pub called the Albert next to the 'Ministry of Justice'.
I tried to get into Westminster Abbey like countless others, willing to pay a tenner, only to be told that it was closed due to a wreath laying ceremony for the Chilean Navy. Westminster Cathedral was also closed for security reasons due to a speech planned much later on by Tony Blair.
Parliament looked unwelcoming to visitors; I have rarely seen so many machine guns and CCTV cameras in such a small space, and the lines of the building at ground level are now concealed by solid black gates to protect against truck bombs.
I went into the park and took a couple of pictures of the river; everything was flat and grey. Wandering up Whitehall other tourists were engaged in fruitless conversation with the coppers at the gates of Downing Street.
"No" said the policeman "I don't think anyone is ever allowed in there". It was possible to see a couple of limousines parked in the road, but that was all.
I pushed on past the tacky overpriced shops (memory card for fifteen quid anyone?) and dodgy looking pubs to Trafalgar Square. Thousands of tourists - literally - were here, sitting on the steps. The pigeons seem to have returned too.
I got on a bus, which didn't move thanks to roadworks on Regent Street, so got off and kept walking to Oxford Street. Lots has been written about how one of what should be one of Europe's best shopping venues is tiring of body and draining of spirit, so I won't bore you here. Finally crashed out at the top of John Lewis, where a latte costs £2,10.
Why do visitors come here?

London