The moment you book your holiday. Always. This is so your trip is protected in case you can no longer go away (over one-third of claims are because of this). Lots of people don’t even know that travel insurance covers you for this. It’s a hidden gem.
Or, you save some money and you buy an annual policy. This will work best if you’re travelling at least 2 - 3 times a year. This will cover you for the entire year, as many trips as you want, as long as they are each less than 45 days. Again, lots of people don’t know about this. Save time and money and buy it for the year.