Interesting one this. We get similar reports out on Dartmoor fairly regularly - big black cats, way larger than any domestic animal, and witnesses always say the same thing about the movement, that low fluid walk that's completely unlike a dog or fox.
The sceptics always default to "escaped pet" but these sightings have been consistent for decades in some areas, which doesn't fit that explanation at all.
Few questions for you - how far off the ground was the shoulder height roughly? And did it seem aware of you or just moving through like it had somewhere to be? In my experience the ones people describe here tend to ignore humans completely, almost like they're used to avoiding detection rather than being genuinely wild and reactive.
Would love to know if theres any livestock losses in the area around the same time. Thats often the detail that gets overlooked but it can really help build a picture of whether its a resident animal or just passing through.