Take 2 spanners, place one on the filter side and the other on the nut on the fuel line. Arrange them so that they form a squeezable angle. With your left hand, hold the heads of the spanner in place so they don't fall off the nut and filter. With your right hand in a leather gardening glove, squeeze as hard as you can. Don't worry, you will be able to get it loose. I'm a thin guy, and by squeezing I managed to get it off, while twisting the metal on the nut!
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