How do I get the weight OFF my horse!

She looks pretty good. Winter is coming for most people so right now isnt the best time to be cutting a horses food back.

Agrees with she's fine..

Weight watchers is having a special right now....

She was out of work for 12 years or so, and only recently has she been brought back into work abd been ridden. Over winter, as I said in the normal post, she didn't get much work because we have no where to work her. I don't want to retire her fully, as she is still very capable and she seemed so much happier and youthful when she was in work.
Thanks for the advice, but I would still like to get her weight down even just to the point where her fatty neck is back to normal.

I'm in Aus, its almost summer now =)

Your horse has the look of a horse with insulin resistance. It would be a good idea to discuss this issue with your vet as it's more likely at her age and can lead to laminitis, poor immune system function, etc.

Common recommendations are to limit grazing, cut grains from the diet and provide added nutrition in the form of a protein/vitamin/mineral supplement that is low in non-structural carbohydrates.

I would try a grazing muzzle. I disagree that you should leave her heavy because of her age because of the health risks involved in her being over weight. Now, she doesn't look that heavy, but I agree she is needs to drop some pounds. I would try a grazing muzzle every other day, and if you see she looses too much, cut back on its use, and it she doesn't use enough, do every day.
Also, fit is very important - there was a great article in Equus about it a few months back.