A National Lottery spokesman said: "We're desperate to find this mystery ticket-holder and unite them with their winnings. This amazing jackpot prize could really make a huge difference to somebody's life.
"We're urging everyone who bought a ticket in this area to check their old tickets again or look anywhere a missing ticket could be hiding."
To jog memories, Get Up (Rattle) by Bingo Players featuring Far East Movement was No 1 in the UK singles chart, while Biffy Clyro topped the album charts with Opposites.
Football fans may remember that local side Gillingham were in action on the day of the Lotto draw in League Two. The Gills travelled to Bradford City and managed a 1-0 win.
Away from sport, comedian Mark Watson performed at the Stag Community Arts Centre in Sevenoaks on February 7.
Anyone who believes they have the winning ticket for any of the National Lottery draws within the 180-day deadline should call the National Lottery line on 0845 910 0000.