On Monday Charlie Bean begins a whistle-stop tour of Britain to explain the arcane mysteries of quantitative easing (QE). The Bank of England’s Deputy Governor is inviting questions from the public on this fashionable form of financial alchemy, which consists of creating money through the click of a mouse in Threadneedle Street and injecting it into the wider economy by buying government bonds.

While unkind souls such as myself insist on calling this debasing the currency, QE is seen as wholly respectable, enabling the authorities to stimulate the economy once the preferred policy lever, the interest-rate throttle, has been pushed flat to the floor and can’t go any further.

The awkward questions for Mr Bean will not be about QE but its opposite, quantitative tightening (QT). For like a mousetrap, the policy is infinitely easier to get into than out of. At some point, the Bank will face evidence of inflation and then it will have the unlovely choice of which of two levers to pull — QT or a base-rate rise.

QT will be difficult. How on earth will the Bank set about selling £125 billion of government and other bonds at the same time as the cash-strapped Government is itself desperately trying to raise money by selling its own new bonds? The gilts market won’t tolerate it. Just the Bank’s statement this week that there would be no immediate additional QE sent traders into a panic.

The Bank’s own pamphlet on understanding QE contains 13 pages on the miracle of quantitative easing and one paltry sentence on reversing it.

QE has been presented as a free lunch. It is not. The base rate will probably have to go higher than it would otherwise because of the impossibility of reversing it. Savers will have something to cheer about but the question for Mr Bean from millions of mortgage payers should be: how much higher are mortgage bills going to go because of QE?

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