Why is the BBC denominating UK politics stories in dollars?

There’s a rather odd line in today’s BBC story about Members of Parliament and their expenses. Talking about Gordon Brown’s repayment of expenses he had previously claimed, the BBC reports:

In Mr Brown’s case the £12,415 ($19,614) is made up of £10,716 for cleaning claims above Sir Thomas’s £2,000 annual limit, £302 spent on gardening above the annual £1,000 limit recommended and a £1,396 decorating bill that was “inadvertently assigned by error to two quarters”.

Why give the sum in dollars? The US is certainly a big media market and I’m all for the BBC having an international audience, both for the positive influence a high-quality media outlet can have in many countries and also because advertising revenue from its international audience helps pay for public services for us in the UK.

But it does seem a bit rum to give a figure in dollars on this story.