I've been reading our copy of the Friends of the Park history book. Amongst other things It gives a history-walk type tour around the park talking about various present and now disappeared features, such as the circus, banquetting hall, and the Japanese village, which show how different a place it has been at different times.
A fascinating, and totally unknown to me, item in it is the airship built on the football field around 1905. The large shed in which it was built appears from various photos to be right on the edge of the boating pool. The airship was started under a contract with the army, but the then owners of the palace paid for the building of the shed in the hope that the whole business could be made into a paying public spectacle. It was built under the leadership of Dr Francis Barton, a GP fascinated by flight. It wasn't a smooth running project and took 3 or 4 years. Barton made his own hydrogen at the site and one night blew up his hydrogen generator by overworking it. It looks as if the explosion would have blown in the windows of our house had it been there then. He also got into trouble with the council for pouring toxic waste into the sewers. The press reports of these goings on are on this interesting blog.
However - at this time and in this shed were built not one but two airships. During a period when Barton wasn't doing much, the shed was used by Captain William Beedle, another freelance airship builder, to build his own machine, which flew once at the palace, and appears mistakenly in some photos as the Barton airship. This part of the story is told here and here. The first of these two blogs tries to fix the actual site of the shed, but if this is right, it suggests the fall away of the ground onto the football field was not as it now in around 1900: but it's not all that clear. It seems more likely that the shed is on the flatter ground about to become Vallance Road. Vallance Road appears in the 1912 OS map, but not 1894, when that area was part of the park with a permanent circus building. Around 1900 it may have been on the way to being sold off to developers but not yet built on, and an airship factory would have been a profitable temporary use.