After a while, the rabbit seemed happy with the burrow and then she kept running up to the top of the garden where I strimmed the grass on Saturday. There she gathered up clumps of grass in her mouth and ran back to the burrow before emerging to get some more. It was like having a nature documentary going on outside. Of course then I had to Google about baby rabbits and discovered that (unlike what I had previously thought) the mother doesn't stay with the babies, but just covers them up and leaves them for most of the day, only returning once or at most twice, usually in the small hours of the morning, to feed them. That's actually a relief because I didn't want to scare her away from the babies, but neither did I want to have to avoid going out into the garden, not when there will soon be blackberries to pick.
Following a tip on one of the web pages, I have laid a couple of small twigs across the top of the burrow in a distinctive pattern. If mother rabbit returns to feed the babies, she will disturb the twigs and I will know that there genuinely is a little rabbit family living in our garden.