Discovering real tone

"I was working at The Power Plant in Willesden, London.  We provided in-house 24 hour technical support to the studios.  I usually took the late shifts so I'd hang around in the evenings - there was a bar and restaurant, and three studios so lot's of activity and music. When nothing need fixing I'd spend my time in the maintenance room working on my rig.  It was around 1990 and I was using a 100 watt Marshall stack with a heavily modified JMP Super Lead MKII head.  High gain preamplifier distortion was the thing and at one point my head had three channels, two FX loops and a four button foot switch.  I was also modifying amps for other guitar players and in part payment for one job I was given an old AC15 - beige, red panel and single 12" speaker.  The guy had only a little cash and this low powered amp was of no use to him.  I wasn't overly pleased about being offered this small old amp instead of money but charitably I still accepted his offer.
One afternoon a tape op came into the maintenance room with an AC30.  "Can you fix this? - It's for Robin (Millar)'s guitarist in Studio 3 - it's not sounding right".  After ten minutes on the bench I figured the AC30 needed some new valves so I drove round to Cricklewood Electronics and bought a set.  New valves installed and a few other things sorted, I humped the amp up the stairs to Studio 3.  Robin was sat there with his guitar player.  They were recording some demos - for a forthcoming Randy Crawford album I think.  The newly serviced amp was set up and I hung around to check they were happy with it.  The guitarist plugged in his strat, turned up the amp and started to play some bluesy licks.  I was totally blown away with the tone and creamy but articulate tone!  And when he backed off the volume control on the guitar he produced the most wonderful chiming clean tone.  The guitarist was Robbie McIntosh and within a week I had bought a strat and the AC15 had been fired up!"  The Marshall took a back seat as I lost myself in the organic nature of this wonderful combination of single coil pickups and a simple valve amplifier that gave me the most satisfying playing experience I'd ever had.