Ruth Kelly’s decision to quit Gordon Brown’s Cabinet to devote more of her time to raising her four children has, predictably, made Westminster dizzy with speculation as to her true motives.

The instinct of political pundits is that there is generally more than meets the eye, or less than meets the eye. Accepting what you see is only for the credulous. So Westminster-watchers, twitchy for a fresh fix of intrigue after coming down from their Labour conference high, wondered if Ms Kelly’s resignation wasn’t further confirmation that Mr Brown’s Cabinet is about to implode.

But is there not adequate evidence that she may be leaving for the reasons she has given for us to allow her the grace of being believed?

Yes, she was about to be eased out in an imminent Cabinet reshuffle. Yes, she may lose her marginal seat at the next election. Yes, she is a Catholic queasy about the Government’s stance on stem-cell research. Yes, she far preferred working for Tony Blair than for Mr Brown.

But a minister’s hours are long. The workload is taxing. To your young children you become that mythical Westminster beast — half Man, half Red Box. That you can be in a trade where it is considered normal to announce a minister’s resignation at a press conference at 3am (as happened with Ms Kelly) is surely reason enough to investigate a more family-tolerant lifestyle.

John Lennon said that life is what happens when you’re making other plans. Ms Kelly has evidently decided that families are what grow up when you’re tied up late at the office.

We cannot salute the nuclear family and then smirk at any politician who would rather minister to one than to a Cabinet portfolio.