The footpaths in Hulne Park are all very accessible (although dogs and bicycles aren't allowed) and this makes for a pleasant. If you do the whole Blue circuit, it's approximately 7 miles in total... that sounds like a long way but it doesn't feel like it!
Please note - the park is open between 11am and sunset each day. At certain times Hulne Park may be closed to visitors - usually during the winter pheasant shooting season.
Infomation on Hulne Park and the walking routes can be found here:
http://www.northumberlandestates.co.uk/the-estate/walks-trails/