What backs up the pound sterling?

Question

I know that the US dollar used to be backed up by gold and silver, then the 70's came and it was oil due to deals with the the House of Suad (which is an illusion) because nothing backs the dollar but trust.

So what backs up the British Pound and Euro while we're at it.

I invite your answers

Answer 1

The Bank of England and the European Central Bank I would imagine?

Answer 2

last i heard it is gold