The Senior Cat is a

"worry wart". I know of nobody else - not even myself - who worries as much as he does. 
My two godchildren and their mother have been to visit this last weekend. There was a holiday on Monday and, because of school holidays in Singapore (where they live) they were here on Tuesday as well. 
My sister and I took them up to the wildlife reserve in the hills behind us. It is a marvellous place for children. They can feed the animals (all native animals) and pat most of them. The Senior Cat was anxious about that. We wouldn't let my godson get bitten or scratched by anything would we? He worried until we returned safely.
Yesterday they came for lunch before going off to the airport and their flight home. He worried about the taxi taking them to the airport on time. (It arrived in plenty of time.)
The Senior Cat also taught my godson a couple of "magic tricks". One involves the use of a small steel disc. Much fun was had. Late last evening the Senior Cat found a microscopic cut on his hand. He rushed into me. What if it was from a sharp edge on the disc? He wanted to ring their mother immediately. By then it would have been very late indeed. I said "NO!" very firmly and sent him to bed.
He was up at the crack of dawn (for him) wanting to ring them. I said it was much too early to call them. They would still be asleep. I also said I had (a) had an e-mail to say they had arrived safely and (b) that young godson had already shown his grandparents the tricks without coming to any harm.
He is now prowling like a caged lion waiting for it to be late enough to call them because he is still worried.
The fact that I have already sent an e-mail and asked his mother to re-check the disc is beside the point. "But she might not have read your e-mail!" 
He will have to speak to her himself. Nothing I can do or say will stop him unnecessarily worrying. 
I am seriously glad he is no longer responsible for an entire school of children!