Everybody knows heard the old saying, there's no such thing as a free lunch. Everybody, that is, except the Bank of England.

Perhaps its officials have enjoyed so many free lunches themselves, that they thought it didn't apply to them.

The BoE reckoned it had discovered the financial equivalent of a free lunch, in the wake of the financial crisis.

It dug the UK economy out of the hole left by the greedy banks, through the magical money mechanism known as quantitative easing (QE).

This involved buying bonds to bring down long-term interest rates and encourage consumers and businesses to borrow and spend money.

You can read about the technicalities on the BoE website, although interestingly there is little mention of the potential downside. So let me fill you in.

The UK government issued the bonds, and the BoE bought them. Which sounds a bit dodgy, when you think about it for half a second.

Especially since the programme was supposed to last just a few months, but in total the BoE bought a staggering £895bn of bonds, of which £875bn were UK government bonds.

Now BoE governor Andrew Bailey is desperate to curb inflation (partly fuelled by this stimulus) by driving up interest rates and selling bonds.

This process is known as quantitative tightening (QT), and it’s only now that we are discovering the cost of the BoE’s largesse.

It’s a cool £180bn. Or it might be £200bn. We still don’t know for sure.

That's roughly the cost of running the NHS in England in the current financial year. And double the annual bill for the UK’s state pension.

In technical terms, then, it's quite a lot of money. That would have been better spent elsewhere.

When QE was first launched in March 2009, the Government said it would cover any losses the BoE suffered as a result of its bond buying spree.

That was generous of it. Perhaps HM Treasury believes in free lunches, too.

At first this wasn’t a worry. QE did its job, and the UK was spared an economic and social meltdown, too.

For a time, it looked like we might even make a profit on QE.

Bond prices and interest rates move in opposite directions. When interest rates fall, bond prices rise (and vice versa).

So with interest rates staying low for more than a decade, the BoE made a £120bn profit by selling bonds at a higher price than it paid for them.

Now that base rates have shot up from 0.1 per cent to four percent, it is heading for a net loss.

HM Treasury has just asked Parliament to make good on its promise to pay it.

Although when I say Parliament, I mean taxpayers.

READ MORE: BoE leaves taxpayers with £200bn bill and you will pay it

We still don't know the total loss, which will depend on bond market conditions. But the higher interest rates rise, the bigger it will be.

Which is a worry given that the Bank of England is set to increase base rates yet again to 4.25 percent at its next meeting in March, and potentially to 4.50 percent in the meeting after that.

The request to borrow £200bn (let’s repeat that, £200bn!!) was buried in Treasury documents, but discovered by The Daily Telegraph.

As I wrote last year (and many times before), QE was always a dangerous policy and continued for far too long.

We paid billions to bail out the banks and now we will be paying billions more to cover the cost of the measures introduced to save the economy.

More than a decade of low interest rates also inflated house prices and stock markets, leaving them vulnerable today.

And it hammered savers, by destroying interest rates on their cash deposits.

What most people didn't realise was at the end of all of that, there was going to be a huge bill to pay.

QE was never a free lunch. Ordinary people have been picking up the tab ever since.

Now it's the turn of taxpayers.