The barbarians are again at the gates. The announcement of the largest ever private equity buy-out of a public company – the $45bn takeover of TXU, one of the largest utilities in the US, by Kohlberg Kravis Roberts and Texas Pacific – confirms the trend. To its defenders, private equity makes companies more efficient. To its attackers, its practitioners are financial manipulators and asset-strippers.

So who is right? An obvious answer is that private equity is a growing activity in which willing sellers meet willing buyers. If it prospers, it must be profitable. If it is profitable, it should also be adding value.