 A memorial tablet to Harrison was unveiled in Westminster Abbey on 24 March 2006, finally recognising him as a worthy companion to his friend George Graham and Thomas Tompion, 'The Father of English Watchmaking', who are both buried in the Abbey.The memorial shows a meridian line (line of constant longitude) in two metals to highlight Harrison's most widespread invention, the bimetallic strip thermometer.The strip is engraved with its own longitude of 0 degrees, 7 minutes and 35 seconds West.