Once started, this train of memories proved difficult to interrupt. Later a Conservative backbencher pressed the minister on how he intended to retain ethnic minority recruits once they had been persuaded to join up. This was a coded reference to the fact that being used as an ad hoc lavatory brush by some Neanderthal in khaki doesn't give a very encouraging notion of career prospects. But for me it also brought back another memory I would have preferred to remain buried - the image of the ablution arrangements at an army training camp somewhere in the Scottish Highlands. The lavatory here consisted of an immense clay pipe with a row of openings along the top - something like a giant ocarina - on which costive cadets would perch. It sloped gently from one end to the other so that the deposits of your comrades would slide slowly past beneath you on a thin trickle of water as you attempted to overcome the paralysing rictus of the sphincter brought on by this unnerving form of evacuation.
I don't want to harp on about this unusual piece of sanitaryware but it also came to mind when I was watching John Redwood, glumly sedentary as Peter Mandelson read out his statement on the future of the Post Office. Usually ministerial statements provoke more reaction from the opposition. Some particularly noxious assertion will glide past and the relevant Shadow will leap up and shout the Parliamentary equivalent of "My God, that's an absolute whopper!" Then after a bit of argy-bargy production will resume again. But yesterday Mr Redwood waited until the last gaseous toot had faded ("We are ushering in the start of a confident, bright new dawn for the Post Office") before rising on the attack.
Encounters between Mr Mandelson and Mr Redwood have taken on the air of a genuine grudge match, a sense of direct antagonism which is accentuated by their physical similarities. Both men are tall and lean, dark-haired and narrow of visage, both can be distinctly mechanical in their manner. Indeed it is possible at times to imagine they have emerged from the same production line - Mr Mandelson being a later design evolution of the Redwood prototype, with sleeker streamlining and enhanced Irony and Guile features. Certainly some design work was necessary. It's clear, for instance, that the humour chip is defective in the older model. "It is a second class statement and it won't be delivered on time," said Mr Redwood, inserting a brief ad-lib into his prepared riposte. Mr Mandelson offered a retaliatory postal bon mot: his remarks, he said, "should be stamped 'Return to Sender' and sent back to Central Office". I thought of the ocarina, again - and of its most alarming feature. It had no chain.