Chorleywood Estate was once a private mansion with substantial grounds. Now, it is open to the public. Most of it is only accessible by foot, cycle or horseback. We were heading for one particular bit, a green bank alongside a shallow stretch of river where families like to come on sunny days. The river is very shallow and it's ideal for children, and since it is cut off from the road, there is no risk of traffic.
The place was a little busier than usual - as you'd expect on a holiday weekend - and there were enough other families and kids there for them all to find friends, and for adults to watch out for the kids.

We could have taken the tube to Chorleywood, but we chose to drive. Maybe not such a great idea since A got sick. But anyway, we parked about half a mile or so from the river and walked the rest of the way on a nice little track, carrying the picnic. It wasn't arduous (but then, it wasn't a very large picnic).
They found their own amusements. They fished for tiddlers and spotted some larger fish, too. One of the kids had brought along a bucket and several had nets.
... and played in inflatable boats.
And the charming little river is much nicer than a man made paddling pool.

