Not a single’s specialist holiday firm, but, if you like wildlife, I can recommend Naturetrek holidays. The last group one we went on had eleven people - two couples and the rest for one reason or another all singles. (One chap had left his wife behind because she didn’t like birds and wildlife and another lady’s husband had gone on a golfing holiday with his mates.)
They do charge single supplement though unless you’re prepared to share with another single person.
Problems in Harry and Meghan Marriage


