My hand holds a stick of vine charcoal.
With it, I block in the figure of a young man.
His long body sprawls across the couch, relaxed as a sleeping dog but his neck muscles tense, holding his head in a position to watch as I sketch.
My gaze tracks a relentless path between him and the cartridge paper clipped to a board on my easel.
Dropping the charcoal to my palette, I wipe my fingers with a damp cloth, my gaze fixed on the silent sitter.
Taking up a razor blade, I shave a slice from a wedge of blue, soft eraser.
With this, I wipe the charcoal 'flesh' of his neck from above the collar suggested by six swift lines on the white paper.
Line alone constructs the rest of his white clothes.
The body beneath vanishes, its vigour apparent only when I shade some suggestive folds into the whiteness.
His shoes become leather as my thumb smudges charcoal over their outlines.
I shine them with dabs from the eraser.
Now, I begin modelling cheekbones and deep orbital pits where those keen eyes will come to life.
Next comes the delicate work of setting the fleshy parts around the mouth.
A long-drawn breath sends confidence flooding my veins, guiding my wrist as it swings from the shoulder to place that enigmatic line where the lips meet.
A flick of rich darkness marks nostrils and the corners of the mouth.
One stroke of eraser indicates the nasal bone beneath the nose.
At last, I zero in on the eyes.
Short lines, caressed along the bony arch above, describe lively eyebrows.
A collaboration of charcoal and eraser forms eyelids.
Eyelashes on the near-side appear indistinct, needing only a swipe of line.
The pupil is a perfect circle in its eyeball's shaded sphere.
By contrast, the angle of the far-side eye distorts its pupil into an ellipse.
More pronounced eyelashes throw that eyeball into deep shadow.
I cut a sliver of eraser, rolling it between my fingers to form a tiny cylinder.
With its tip, I lift one spot from the shaded cornea.
These eyes spark with life!

• I wake.
  The clock shows 05.
  22.
  Time enough to lie abed, replaying the dream.
  Rolling out, I snatch up my notepad and scribble a record, still clear in memory.
  

I recognise the man I sketched as actor Benedict Cumberbatch, whom I'd seen on TV during my lunch break.
His fine performance in the role of Stephen Hawking, was the obvious catalyst for my dream.
Yet, I'm unlikely ever to meet, much less paint him.

• Why the dream?

Well, scientific evidence shows our brain processes data during the REM, or 'Rapid Eye Movement' stage of sleep, when we dream.
Not only does the brain scan all received data, it sorts important information from trivia.
Priority files are prepared for storage in our long-term memory.

• Guess how the brain achieves this? Yes, it uses the mind to tell us a story.
  

This dream holds a strong message for portrait artists: get the bare facts of your sitter's appearance down, in black and white, making many sketches before you begin a portrait painting.
I did this throughout my career, never thinking about the process.
In the dream, as in the studio, I didn't think about the person as I sketched him.
A naked Brad Pitt might stand in for my subject.
I was engrossed only with drawing an accurate description.
Now, I can pass the dream's lesson on to you.
If you get the 'likeness' right, the sitter's personality will shine through.