You are joining someone in a foreign capital who is hosting you for a fine meal at their upscale home, then out to a fancy hotel spot for some jazz music. You will be met by a private boatman to ferry you there.
They have specified ‘No shorts, No flip flops! Smart Casual.’
Is a tshirt an appropriate garment to wear? How about a long sleeve version with, y’know a couple of buttons and a placket at the neck?
I don’t think a t-shirt would be appropriate. It needs to be a shirt with a collar and I think the type of shirt that needs to be ironed is better than a knit shirt like a polo shirt.
The only way I see a t-shirt working is if you have the personal style, panache, and frankly, money, to wear some kind of graphic t-shirt under a sport coat a laRobert Downey, Jr., and even then I think you have to be Robert Downey, Jr. to pull it off.
My “uniform” for this kind of thing is a neutral colored pair of pants (mostly jean-cut cotton) with a patterned long-sleeved shirt. Depending on perceived level of formality I might leave the shirt un-tucked and roll up the sleeves, or I’ll tuck everything in and wear a sport coat over it.
For me it would depend on how well I know the host, how many other people might be attending, and what the hosts level of formality tends to be. IMHO you rarely go wrong by erring on the side of over-dressing.
Almost everybody in the modern western world dresses better than Americans when it comes to daily attire. Keep that in mind and choose wisely.
My advice:
No crappy dockers (be better than The GAP)
White dress casual shirt is classic (avoid short sleeves unless you’re in the tropics and have the arms to pull it off)
Nice shoes. (No fucking sandals!)
A great casual jacket.
If you are going any place upscale or fancy, then a t-shirt is a no-no. You definitely want a shirt with a collar.
Googling “Smart Casual” I see some younger hunks wearing nice t-shirts, but mainly in combination with a sport coat. But if your hosts are older, I would err on the side of being more conservative.
I personally think I a polo to too casual for what you describe, but I tend to err on the side of overdressing. A nice long sleeve button up shirt, good leather lace up shoes (not gym shoes/trainers), slacks, and a jacket is what I would wear. You can always take off the jacket and roll up the shirt sleeves if everyone else is more casual.
The thing I’m noticing is that this invitation does not appear to be from a close friend. There’s an “upscale home” ,a “fine” meal–(not just a good meal), a fancy hotel…and there’s a private boat (= small yacht?) involved.
Dressing too poorly would be a social faux pas, uncomfortable for your host, embarrassing for everyone (and, in the worst case, ruin the evening by causing you to be refused admittance by the doorman at the fancy hotel.).
Dressing a little too elegantly will not be a faux pas, will not be embarrassing, and will not ruin the evening.