Nothing is resolved, but BHP Billiton’s tilt at PotashCorp already looks like a classic piece of post-crisis M&A.

A quick scan of the year’s biggest deals, compared with those of 2007, shows that opportunities accrue to those with the strongest balance sheets. Investors will tolerate a measure of strategic promiscuity if it comes from a company like BHP, where operating cash flows after interest and tax were more than twice the sum of dividends and net debt in June.

Companies do not necessarily have to be better rated; on average, the top 10 dealmakers in 2007 – many of them banks – had slightly higher credit ratings than 2010’s crop so far. But what they do need is lots of reliable cash-generating assets, and a reputation for using the proceeds wisely. Think triple-B News Corp, trying to mop up minorities in BSkyB, or double-B International Power, merging with GDF Suez. Both have top-quartile returns on invested capital.