At last, I was alone with Derek - though probably not for long - so I decided to take my chance while I could.
As I had done at Linden Lodge, I reached forward and this time as gently as I could, started to improvise a bass-line below what he was doing. The notes were barely audible to me, but Derek was on to them immediately. His left hand shot down to where my fingers had trespassed, shooed the intruders away with a flick, and instantly picked up from where I had left off.
Round 1 to Derek.
Leaving my chair, I walked round to the other side of the piano and starting improvising an ornamented version of the tune high up - as far away as I could from his right hand. In a flash he was there again, defending his territory against this second musical interloper. He pushed my hand out of the way, and, once more, began imitating what I had just played before extending it to fit in with the changes in harmony.
End of Round 2, and Derek was clearly ahead on points.
Still, by following me to the extremes of the keyboard, he had left the middle range of notes temporarily exposed and, surreptitiously leaning over Derek's shoulders, with a feeling of mischievous triumph, I started to add in some chords. My victory was tenuous, however. Without for one moment stopping what he was doing, he tried to push me away with the back of his head. This time, though, I was minded to resist.
'Do you mind if I join in, Derek?'
My words fell on deaf ears. Ignoring me, he pushed with increasing force, all the time continuing to play. His message was unequivocal, so I decided to let him have his own way. For now. As soon as the coast was clear, his hands darted back to the middle of the piano, to fill in the chords that were now missing, before scampering outwards again to catch up with the abandoned tune and bass-line.
'You need an extra hand, Derek', I joked, as in my mind I conceded Round 3 to him. By a knockout.
Then, some months later ...
I decided to start with some five-finger exercises - the foundation of all keyboard technique: just up and down the keys, one note for each finger and the thumb. Would Derek find that sufficiently engaging? How would he react? But these questions were supplanted in my mind by a more immediate problem: how was I going to be able to get at the piano for long enough to play the notes that he was supposed to be copying?
Sitting next to him on the piano stool, I tried holding both his wrists with my left hand to give my right free rein on the keyboard. I reckoned that I only needed about ten seconds. But that was nine too many for Derek. He wriggled out of my grip in no time and struck the C that I had managed to play before being overwhelmed. I was afraid of hurting him if I held his wrists any tighter, so I had to try something else.
'Right, Derek', I declared, 'we're going to play a game. You're going to sit over the other side of the room while I play something on the piano, then you can come over and see if you can copy it.'
I didn't really expect him to understand what I'd said, but in any case, without waiting to see his reaction, I picked him up and plopped him down on the floor at the far end of the nursery. I strode back to the piano and quickly played the five-finger exercise. I'd only just finished when Derek, who'd been amazingly quick out of the starting blocks and had fairly scuttled across the room was pushing me out of the way. That done, he reached across the stool, and played what I had - well, a version of it. He used both hands to play a series of chords, up and down. I had to laugh at his antics.
Then he stopped, waiting. This was a game whose rules he had somehow immediately grasped.
So I picked him up again, sat him as far away as I could from the piano, raced back and played the exercise again - this time starting on the next note up, C sharp. Again, my thumb was barely off the last key when Derek was back with his response.
And so we continued up the chromatic scale, until we'd tackled all twelve different keys. That brought us back to C, and it felt right to stop there. Derek seemed to sense that feeling of completion too, and he was content to return to his familiar routine of taking requests for pieces to play.
He still wouldn't let me join in, I noticed, but I didn't mind: I was convinced that the five-finger-exercise game had provided the breakthrough that I had been looking for.
Now I had something to build on - the beginning of the relationship between us that I had mentioned to Nanny.