Identity Unknown

While walking in the local town park today, I passed a group of people who were gathered around a car looking at a book of some description. I didn't take too much notice of them as I was busy taking photos and I thought maybe they were members of the park committee doing plant counts or something.
On my way back along the driveway through the park, one of the group stopped me. I hadn't noticed but it was an old friend and ex boss, Ron, looking a little older older than when I last saw him but still obviously fit , active and interested in everything. He must be in his eighties now. He used to be principal of the primary school my kids went to and where I had taught for several years back in the 1980s.
He was very interested to see that I was taking pictures in the park because he is , in fact, one of the carers of the park but also a keen photographer and what he and his friends were doing was trying to identify a shrub. It was in full blossom, a couple of meters tall and the flowers were white, similar to hydrangea flowers but each clump was filled with a mass of tiny, creamy white flowers. The larger flowers were unusual in that they had four large petals and one small one at the bottom. I thought it could be a lace- cap hydrangea but it didn't quite match the picture in the book and the leaves were narrower and softer.
After quite a long chat with Ron, he decided that he would take a piece of the shrub into a nursery on his way home and hopefully the nursery staff could help identify it.