It was in Private Eye, which is generally rock fucking solid. Also, unlike most of the British media they don't have a hard on for hurting the BBC as their editor is one of the key talent on one of the BBC's most successful panel shows. Here's what's said to have happened:
- Terrible budgeting/scheduling on the Who production side (not the BBC bosses side) forced the Series 6 split
- Willis employed her boyfriend during the overseas shoots of 'Vampires of Venice' and 'Vincent & The Doctor' and then booked a few weeks off after the filming was finished, staying in Croatia with her bloke at the BBC's expense (and don't forget, non-Brits, that's the taxpayer's money) after filming had wrapped.
- Moffat had to change the episode order & do significant rewrites to Series 6 to give it a natural mid-series break point
- Tracie Simpson (RTD Specials, Series 5) and Peter Bennett (a stalwart of the show, from 'Bad Wolf' through to 'The Big Bang') were both asked to return for Series 6 but refused due to the way they'd been treated by Wenger/Willis, and were a massive loss from production and for the first time without a 'handover' period teaching their replacement (ie Simpson was taught by Collinson before he left)
In the same issue they reported that the series 6 fuck ups were having a knock-on effect, and as a result we wouldn't get a full series in 2012, but a series of specials ala 2009... which actually didn't end up being too far from the truth. This was in June 2011. By this point Wenger had already gone, and less than a month later Willis followed. They're also the only higher-up people from Who to not get promoted massively after leaving the show - Wenger was shuffled sideways within the BBC, and Willis went back to her old job at Kudos (where she'd previously Produced Ashes to Ashes). All very telling. Still, if it's all true, good riddance. Quality difference in this year's episodes has been substantial.