Using the BBC news rss feed - higher res images urls

Does anyone know if there is a way to get higher resolution images in the BBC news feed rather than the (I think) 141 x 80 size images that come with each article. I know these photos exist because they use them on the website themselves. I've noticed that开发者_JAVA百科 some simply need to have the number prefixed and suffixed with underscores changed by one or two, but others have what seem random numbers.

My question is, are there, somewhere, alternative URLs or some kind of algorithm I can use?

Sorry if this doesn't make much sense but if you want to know what I mean it might be worth taking a look at the raw XML of the news feeds.

Thanks in advance