After two days spent wrestling with the problem of how to distinguish the essential from the desirable from the urgent to ensure that a programme really is focused on driving the highest value first, I realised that a perfect encapsulation of one element of the problem was to be found just down the corridor from the meeting room.

Here is a space to wash your hands. It contains basins, each with taps, soap dispensers and hand dryers. Everything is there to complete the hand washing task successfully. And it all works: there is water in the taps, soap in the dispensers and air in the dryers.

But it all works just a little oddly.

The soap dispenser is automatic: it spits out a froth of soap when you put your hand underneath. The tap works on a plunger: water spurts out when you press the plunger down. It gushes so fiercely and the soap is so frothy that it instantly washes the soap away before it can do anything useful. And then it stops with a disconcerting clanking noise from somewhere round the back, with a delay so short that it took me three bursts of water, even once the soap was under control. The hand dryers are automatic too, sensitive to hands being placed underneath them – so sensitive that they stop if your hands move from a sensor area which seems to be a few millimetres square.

It all works, my hands were clean by the end. The functional requirement had been delivered.

But that’s why functional completeness should never be confused with experience adequacy.