songs that Mark plays with a plectrum

[dmg]

It is David indeed http://www.pickwithers.co.uk/

ah yes indeed, the text on wikipedia is surely a coy/taste from here

I didn't know this. It's not mentionned in the Oldfield book (like Ruth is not mentionned neither), and noone booklet got his real first name

indeed, Pick sounds like a nickname, but often in booklets, nicknames are between quotation marks, like e.g. Calvin "fuzzy" samuel, Donald "duck" dunn, franck "poncho" sampedro, chris "whipper" Layton, etc...
sometimes so you can read Philip Collins, Stephen Hackett, etc...even  EC's 2nd first name (patrick) features in his album booklets, so it's strange that Pick Withers was never quoted with his real first name in any record

...and Alan "Hurricane" Clark!