Here's a clip of a much younger John Williams playing fingerstyle electric in his group Sky.
Search Youtube for "SKY - Cannonball (live)"
And another of kevin Peek, also fingerstyle, while JW plays his fabulous Ovation - on BBC's Top of the Pops
Search Youtube for "Sky - Toccata"
In a TV interview in his Sky days, Williams was asked the difference between playing classical and electric. He said it was the left hand - he really admired the way electric players zoomed all over the fretboard seemingly effortlessly. Then, when he played one, he discovered the action was so low, it actually was effortless - so he was less impressed.