Americans have a similar leather wax with a good reputation from vintage times forward, the name of which now escapes me.
Andre, John, there is another option I have used to waterproof leather for 55 years: Sno-Seal.
The tin promises leather protection from rain, snow, salt, sun; the original beeswax waterproofing. Mile warmth helpt it absorb, excess is buffed off with a clean, soft cloth. Instructions say, "Beeswax waterproofing lubricates leather and protects against dryiomg and deterioriation far longer than greases, oils, and animal fats. Sno-Seal is a natural wax and, unlike other products, will never weaken, decay, or break down leather or stitchings and seams. Caution: Will somewhat darken leather; spot test if appearance is important". I have found Sno-Seal to be a valuable adjunct for use on my black saddles. I have not used it on my one Honey Brown model as I don't want it to darken as much as I know it would with Sno-Seal.
See...
https://atsko.com/product/sno-seal-wax-8-oz-jar/https://www.amazon.com/s?k=sno+seal&channelId=520&clpRedir=Y&plpRedirect=mhFallbackAvailable from Amazon Canada as well...
https://www.amazon.ca/s?k=Sno-Seal&crid=F5Z4IT6ASXZH&sprefix=sno-sea%2Caps%2C363&ref=nb_sb_noss_2 I think it is too pricey due to the added tariffs and would not buy it on principle if I lived outside my borders.
I always treat my Brooks leather saddles first with Proofide (now white cream, I preferred the older red formula that smelled much stronger), then after some use, Sno-Seal for regular winter riding. I lay on a thin coat of Sno-Seal to guard against water drops in between my dismounts and slapping on the saddle cover (I don't ride on the cover per Brooks' caution, as Andre notes). I have found the Sno-Seal polishes out to a high gloss under my cycling shorts, then thins out and needs reapplication in time. It lasts longer in winter when I ride less often. I use it primarily on the Brooks B.17 fitted to my commuter Fixie. I don't use it in summer when I am likely to produce a lot more sweat and a "waterproofed" saddle has much less appeal.
Best, Dan.