Softbank paid $20.1 billion in a takeover of Sprint Nextel, America’s third-largest mobile carrier. Softbank’s founder, Masayoshi Son, is a billionaire entrepreneur and not a ladder-climbing company boss or salaryman. He is making corporate Japan’s largest-ever foreign acquisition, which he admits is a big gamble. He is financing it through Softbank’s own cash and debt, rather than hitting up shareholders.

Japan Inc has made a record amount of purchases abroad this year, partly because of the growing realisation that population shrinkage may permanently reduce the size of its domestic market. Mr Son pointed out that demographic factors alone might make not buying Sprint more risky than buying it.

Stephen Givens, a Tokyo-based M and A consultant, says Mr Son is overpaying for a company with a weak position in a duopolistic market. He is mistakenly focusing on acquiring mobile networks whose value can quickly disappear.