An obituary for Dr Mark Blackburn (1953-2011), prepared for the British Numismatic Journal, has been made available electronically in advance of its publication. It can be found here.
[Edit: 30/09/11] Another obituary for Mark appeared in the Guardian on 29th September (online edition; it appeared in the paper edition on Friday 30th September) and can be found here.
[Further edit: 30/09/11] Mark is also the lead obituary in today's Times (p. 64 of the paper edition; accessing the online edition of The Times requires a subscription).
[Further edit: 26/10/11] Mark's obituary appeared today in the Telegraph.