Well - that has let a goat into the garden (*)! Interrail have announced a sale on international train rover tickets buy by the end of this month, and save anything up to 50% on the normal price which is (for Lisa and me and our use anyway) already good value.

Purchase by the end of September, for activation within 11 months later (so by end of August 2027).

Interrail Global Pass, promotion prices
Example - 4 days within 1 month, 2nd class - £209.00 (Adult), £188.00 (Senior)
Travel on as many trains as you like on each of your 4 travel days – perfect for visiting 3-5 destinations.
Example - 3 months, continuous, 1st class - £540.00 (Adult), £485.00 (Senior)
Travel on as many trains as you like on each of 90 days.
* Covers most trains in 33 countries. 
* Just 2 days to / from / within your own country - "outbound" and "inbound"
* You can use your travel days any time within 1 month of your start date.
* Seat reservations may be required for some trains, at an extra cost.
* One Pass. No fixed route.
* Take the long way around Europe, with up to 11 months to begin your trip.
* Promo Passes are 100% refundable or exchangeable within 7 days (0% after).

Small print -
* does NOT include mandatory reservations (nor optional ones), sleeper train and other surcharges where they are needed.  Most of Europe can be covered without / very limited in Spain and somewhat limited in France, and on many tourist and heritage lines.  * Does not include local metros and tram networks, nor buses - but there are some reductions on some ferries. 
* Does not include long distance coaches nor airline flights if you use them
* Does not include travel insurance, nor board, lodgings, entry to museums, and other things you do / use while away
* Does not include costs of roaming on your phone, or internet connections unless free on trains
* Does not include cost of kennels for pets, dog, cat, budgie and house sitters
* Does not include cost of gifts you bring back for loved ones, family, colleagues and friends
In other words, the pass is likely to be only a small part of your outlay.

Web site - https://www.interrail.com/en . I am NOT normally someone who rushes to buy in a sale, and especially one with cancellation terms like these.  However, to me this is not a normal sale - it's a product I have bought in the past, know well, and will be buying again in the next few days. And, no, I get no commission ;-)

(*) The idiom:

Russian - Let a goat into the garden
Dutch - Throwing the bat into the chicken shed.
French - Throwing a cobblestone into the pond
Spanish - To disturb the dovcote
English - Put the cat amongst the pidgeons

In colonial India, a popular pastime was to put a wild cat in a pen with pigeons. Bets would be made on how many birds the cat would bring down with one paw-swipe. The period of the British colonisation of India may have introduced this concept, and hence the phrase to the English language.