What is symbolic about the photo of St. Clement's?

The photo of St. Clement's Church is a symbol of the past.

Yes, he thought again, he would come back. He would buy further scraps of beautiful rubbish. He would buy the engraving of St Clement Danes, take it out of its frame, and carry it home concealed under the jacket of his overalls.

‘It’s a church, or at least it used to be. St Clement Danes its name was.’ The fragment of rhyme that Mr Charrington had taught him came back into his head, and he added half-nostalgically: ‘Oranges and lemons, say the bells of St Clement’s!’