The "marital coercion" defense

One of the ways in which the legal system treated men as the head of a household was not just in the form of rights but also in the form of responsibilities, and I recently discovered in an article in The Guardian that one such law was still on the books in the UK as of 2013. What does (or perhaps now did) it cover?

The Law Commission, which advises the government on law reform, recommended as long ago as 1977 that marital coercion should be abolished as a defence – though a wife who committed an offence under pressure from her husband might still have a defence under the law of duress. Under English common law – the law laid down by the judges over the centuries – there was a presumption (which could be challenged) that a wife who committed an offence in the presence of her husband did so under coercion and therefore should be acquitted. That presumption, which dated back to the time before defendants could give evidence, was abolished in 1925. But the Criminal Justice Act passed that year still said that "on a charge against a wife for any offence other than treason or murder it shall be a good defence to prove that the offence was committed in the presence of, and under the coercion of, the husband".