Bicester is another canonical example. Pronounced like "Mister" with a "B" in place of the "M". I don't think a single native English speaker would correctly pronounce Bicester on their first attempt.
The elision of the 'e' in -cester placenames so that the 'c' and 's' have a single sound is reasonably common e.g. Leicester, Gloucester, Worcester, Towcester, Bicester. So English natives should have a reasonable chance of getting the pronunciation of a previously unseen example correct.
I have heard even Manchester sometimes spoken that way as well, depending on who you’re talking to.
It's not even unreasonable. -caster, -chester, and -cester are related suffixes.
All descending from the Latin "castrum", which means "fort". So if a placename has one of those suffixes, chances are high that it was a Roman settlement.
Godmanchester in Cambridgeshire, although now pronunced by most people as 'God-Man-Chest-Er', used to be pronounced (and may still be by some locals) as Gumster.
And then along comes Cirencester.
Sissiter according to the locals in the old days, Siren when I was growing up in nearby Swindon.
And that's why "Worcester Sauce" is the second most mispronounced culinary term in Germany (after "Stracciatella") *
[*] - according to my made-up-on-the spot stats
Also doesn’t help that it’s actual name is “Worcestershire sauce” which is even more difficult to say.
Now I must know: how do Germans pronounce stracciatella?
Some switch around the "s" and "sh" sounds, so it is pronounced roughly like "shtratsiatella". "st" at the beginning of a word is pronounced as "sht" in German.
If you take the M40 to Bicester, you pass by High Wycombe.