It is proving quite a month for chancellors and shadow chancellors. The symmetry with which Geoffrey Howe, chancellor 1979-83, followed Denis Healey, chancellor 1974-79, both in life and in death (they died within a week of each other) was remarkable.

They both lived to a ripe old age – Healey to 98 and Howe to 88 – and got on famously, despite the oft-quoted jibe by Healey that being attacked by Sir Geoffrey (as he then was) in parliament was like being savaged by a dead sheep.

At a time when Labour’s new shadow chancellor, John McDonnell, is being savaged by the Conservatives, the media and many of his colleagues, it is worth recalling that both Healey and Howe also had baptisms of fire when they themselves were appointed shadow chancellors.

Healey was often accused of rashness in allegedly threatening, in opposition, to “squeeze the rich until the pips squeak”. But he never said it. What he actually said, at Labour’s 1973 annual conference, was: “I warn you, there are going to be howls of anguish from 80,000 rich people, people who are rich enough to pay over 75% on the last slice of their income.”

He got into enough trouble for that, and it was a feature of Howe’s first budget in 1979 that the top rate was reduced from 83% to 60%, where it remained until Nigel Lawson’s budget of 1988, when the top rate came down to 40%.

Sir Geoffrey was often an ineffectual shadow chancellor. As Healey said: “He found this role difficult, as I had, although he was usually able to make some telling points. Fortunately for me, their effect was often blunted by his mumbling diction.” Hence the “dead sheep” remark, which Healey freely admitted was an adaptation of Churchill’s wisecrack that being attacked by Attlee was “like being savaged by a pet lamb”.

The savaging from all sides of McDonnell for his “U-turn” on the fiscal charter is painful and embarrassing, but the shadow chancellor did not get where he is today without being able to take it. He really overstepped the mark when committing himself to George Osborne’s absurd charter, which has been ridiculed even by the chancellor’s sometime cheerleader, my old employer the Financial Times.

One of Osborne’s favourite pursuits is wrongfooting the Labour party. It must be conceded that he is good at it. But it is going to his head: hubris is already in the air, and at some stage he will come a cropper. However, in his desire not to sound weak on the subject of “fiscal responsibility”, McDonnell fell into Osborne’s trap. But the shadow chancellor is plainly aware of Healey’s dictum: “When you are in a hole, don’t dig deeper.”

This silly, but mercifully shortlived, commitment to the charter was the reason why I wrote in my last column that I was not so sure Ed Balls was right to say that McDonnell must be the first shadow chancellor who is to the left of your correspondent.

Of course, just as Osborne was wrong to blame the deficit on Labour’s public spending (much of which was highly beneficial for the nation at large) rather than the banking crisis, so his argument that the Conservatives have always been the party of economic and fiscal responsibility takes some swallowing.

John McDonnell during the debate on the fiscal charter. Photograph: PA

For example, Healey’s chancellorship was bedevilled, among other things, by the aftermath of the Tory “Barber boom” of 1973, when output rose at a record and quite unsustainable rate of 6% a year, and inflation accelerated at a terrifying pace. This latter was the result of a sharp rise in oil prices, for which the 1970-74 government of Edward Heath could not be blamed, but also of the government’s earlier decision to index wage increases to the cost of living, which was well-intentioned but proved disastrous when oil prices quintupled.

The obituary writers have been kind to Howe, who was himself a kind and gentle man. But his embrace of monetarism, and near doubling of VAT, led to a rise in the inflation rate from the 10% he inherited to 20% between 1979 and 1980, and the overvaluation of the pound contributed to the worst recession the UK had experienced since the second world war. Later came Lawson’s unsustainable boom, the ill-timed entry into the European Exchange Rate Mechanism, and another horrible recession.

No, the Conservative party protests too much when it claims to be the custodian of economic competence. And now its obsession with balancing the budget – indeed, aiming for a surplus on both current and capital accounts – promises to make the austerity we have experienced so far look like a vicarage tea party. The damage about to be wreaked by the reductions in tax credits may well prove to be Osborne’s poll tax moment.

There is much for an opposition that gets its act together to oppose. These are early days to be writing off Mr McDonnell. As for that ridiculous charter, the proposal to bind successor governments to fiscal rules is simply not constitutional. The point of macroeconomic policy is to balance the economy, not to balance the budget, let alone run a surplus that in certain circumstances might depress demand.

This government boasts about flexibility in the labour market. You also need flexibility in economic policy. As Lords Healey and Howe knew, there are such things as “events, dear boy”.