Some evenings need to land. The good news is that London has rooms that do the work for you: grand enough to feel like an occasion, warm enough that you can actually talk. The key is matching the room to the moment.
For dinner, our romantic restaurants guide is the place to start, or the grander rooms in our best restaurants in Mayfair. Open with a cocktail at one of the best bars in Mayfair, where the bartending is part of the theatre. And if the night calls for it, the most romantic hotels in London turn an evening into a weekend.
Dress a notch up; it changes how the night feels. Tell the room it is a special occasion when you book, and at this level they will quietly rise to it. The rest is just good company.