I have a continuing correspondence with someone I'll call 'Concerned of Croydon', who first wrote to ask why we keep sending him our supporters magazine when he's happy to give regularly anyway.
He enquired if we had asked our supporters whether they want it, or if they'd prefer the money to go to our "front-line services" (by which I think he means Macmillan nurses - most well known, but only part of what we do). The cost of mailing thousands of donors would indeed fund some of our services, though the cost per donor is very small and it acts as a prompt to people who like to be reminded to give.
But no, we haven't asked our supporters the question he suggests. I am sure most would plump for more services, but if we acted on it the donations that fund the services would fall, and we'd have to devise another method of prompting donors. That would cost as much as producing the magazine.
What I like about Concerned of Croydon is that he asks penetrating questions about things I take for granted - he could be the boy who saw through the emperor's new clothes.
His latest letter suggests, in response to my comment that our fundraising spend is close to the median for our kind of charity, that benchmarking itself is a fudge. "If we are like the others, we cannot be criticised," he says, describing it as a 'safety in numbers' policy that says nothing about the actual scope for improvement. He cites boardroom salaries, which have risen rapidly as a result of benchmarking; near the knuckle, I thought, since only three weeks ago I said in this column that my salary is benchmarked by the trustees.
I'm sure we need to know whether we're ahead of or behind the norm - not only for accountability to the public who fund us, but also for good internal management. Such measures must, however, also be treated with caution, as the notorious charity league tables so clearly showed.
But Concerned makes me wonder whether we're falling into glib use of corporate-speak that actually further removes us from what he thinks of as the front line. 'Corporate goals', 'governance', 'performance management' - what does all that mean to the punter giving £1 on the street or the old lady sending another fiver, who we think of as a 'warm donors'? Words matter - they reflect what you think, which conditions what you do. Concerned's definition of the front line may not be the same as mine, but it's a reminder to look behind the cliche.
Peter Cardy is chief executive of Macmillan Cancer Relief