Mine had a lovely settled routine of 2 hr nap and 10.5 hr night for a good time until 25 months when his nights became shorter and he entered the 1-0 nap drop phase. For us that took several months, he really couldn't don without his 2hr nap, capping was not helpful although I did try it, throwing in a no nap day also didn't help us, really it was 6 months of winging it and riding it out until he was finally ready to drop the nap cold turkey and could cope without. At that point night sleep increased (probably not the first night it often takes time for the night to increase when they drop the nap) to 12 hours - have to say a 12 hour night is AMAZING!!
So, maybe cap the nap like Anna did (you can just reduce nap by 15 mins) or move BT later like I did. Our BT was 8pm for a good while which I was fine with, the period during the 1-0 he began refusing BT so it took up to 9pm to get him to sleep which is why I knew we were on the road to nap dropping. He did not fully drop it until 31 months.