That is a tough one. You actually had a group that I was considering using in a grid myself, so I got that connection - or so I thought. However, your connection was different to mine (Where you had PVGVRF VA BAGNEVB, I had GBJAF BA GUR EVIRE GUNZRF). I think your connection is a bit stronger though, even if it's not unique.

I don't think PNZOEVQTR VF BA GUR EVIRE GUNZRF, but I had only thought of XVATFGBA, WNZNVPN.

You're right actually, PNZOEVQTR VF BA GUR, er... PNZ. I would have had ERNQVAT in my group. I humbly withdraw my objection...

Yes, a nice puzzle indeed. I liked the interesting group of CHECBFR-OHVYG PNCVGNYF especially. Well done!

I got half of it, but very tough indeed. The Calcutta group's link is ingenious, but very obscure. Is it fair to expect people to know this? Similarly with the Cambridge group, why would anyone with 'general knowledge' know this?

Too many possibilities. For instance I knew there had to be an Olympics connection, but since there are three more cities that were Olympic host cities, I never got the right group. Just clicking for minutes to find the right combination is no fun.

Also since everything is cities, multiple valid connections will exist and weren't thought about. Rio, Kolkata, Lagos, Karachi are all major port cities, so why wasn't it accepted?