Possible Clues:

• Chess player to disappear into the blue
• 1972 Match of the Century participant
• Russian world chess master in early 1970s
• Demon on board resorts to raise (very high)
• Boris playing intellectual game, heavens above, admitting 'I haven't a clue'
• 1972 ''Match of the Century'' loser
• Loser to Fischer in 1972's 'Match of the Century'
• He checks the blue pens qualify
• Health resorts -- heaven for one renowned on board
• He has often checked blue pens make the grade