Mike is keen to set off before the sun climbs much higher and is pumping vigorously at the tyre of his mountain bike. Mike has the kind of easy affinity with things mechanical that a duchess might have with a coal scuttle. Thus armed with no more than a simple bicycle pump, he has managed to extract whatever air remains in the tyre so that it is now completely flat.

"Here, let me try," I say indulgently.

These morning bike rides may not be the Tour de France but soft tyres can still cost valuable seconds in the all-important downhill stages. I dismantle both the pump and the valve where it protrudes from the tyre. After several minutes of fiddling and pointless pumping, I am no further forward.

"The pump's knackered or the valve is."

"Gentlemen, please allow me."

We look up to find Ralph, our companion for this morning's towpath ride who has emerged smiling from the bike store kitted out in the most exquisitely vacuuminous lycra cycling gear. His finger is resting on the saddle of a wicked chrome and yellow mountain bike that looks as if it might be self-propelled.

(Thinks. I am in the midst of serious professionals here. If only I can somehow disable the gear change on Ralph's machine and knock out, say, the first twenty-six gears, I might stand a reasonable chance of keeping up.)

Ralph brushes us both aside.

"There's something missing," he says as he takes his turn to dismantle the pump. 

"Errhm. will this help?"

Whilst Ralph has been in repair mode and I have been contemplating the morning's race strategy, Mike has slipped away to Jonathan's Chamber of Secrets, a walk-in cupboard containing tools for every conceivable purpose and some for no conceivable purpose at all.

"I remember now," says Mike, "I was trying to inflate the kids' Scary Green Crocodile by the pool yesterday. The hose-thing on the pump wouldn't fit that plug-thing in the crocodile's
belly-button, so I took this bit out." 

Mike proffers a small but nevertheless essential-looking black rubber grommet.

"I gave up in the end. Pam did it by hand, so to speak."