Beags:
Back to school to learn sums for you, Baldrick!
Nimrod MRA4 was originally 'Nimrod 2000'; 2008-2000 = 8, going on 9 years late
The revised Nimrod MRA4 ISD set in 1998 (4 years prior to the end of commissioning AEOs) was 2005. The current projected ISD is 2011.
I'm not sure about your maths but by my calculations 2011-2005 = 6 years!