Believe it or not, an old army trick was to fill the leather boots with err . . . .human urine . . . no, I am not taking the Pee.
The boots would need to be laced up, filled up and left to soak for about 2 - 4 weeks,
then washed out with warm soapy water
then a light mixture of
dettol - domestos to kill off any wiff, if still stiff a second application of pee,
then the boots would need to be packed with old news-paper to absorb any remaining moisture,
then allowed to dry at room temperature, well away from any heat source such as a radiator as it would shrink and crack
the leather, once dried out a stiff bruising, then a liberal application of dubbing or leather fett to all the upper area.
For the soles, a good stiff brushing, a light sandpapering to the cleats, then a very light application of dubbing,
stand on a pile of old newspapers till the leather absorbs the excess dubbing.
Do not be tempted to apply wd40 as this can eat into the leather material.
Kevin in Deva. :beer: