BBC World Service - Newsday, Thousands Hanged At Syria Prison - Amnesty - Was there really no investigation by the BBC of the claims?

This BBC World Service programme http://www.bbc.co.uk/programmes/p04rcyyz has the lead in text 'A new report by Amnesty International alleges that mass hangings took place every week at Saydnaya prison between September 2011 and December 2015'.

Is that true? What is the source for those figures?

If you're interested in the truth, the BBC clearly aren't, then take a read of this http://newobserveronline.com/amnesty-internationals-syria-report-made-nonsense/   here's an extract:

'A close reading of the report, however, reveals that Amnesty International in fact only claims to have the names of 36 people executed at the prison, and has based the "5,000 to 13,000" figure on a purely theoretical extrapolation drawn from anonymous statements made by opponents of the Assad government—with absolutely no backing evidence whatsoever.'

Do read the whole of that New Observer Online article, my jaw dropped more than once.

Are the BBC really not interested in fact checking news that fits in with their prejudices? I think we know the answer to that question.