Loss of WiFi (Solved) (Hopefully)

[#1]

For some reason the WiFi signal was lost so was unable to connect any tablets or phone to the internet, message in settings showed safe and secure but the internet was not available, I could understand it if we were talking about a single tablet but the same, unable to connect to the internet was showing on a second tablet and phone.
Now it gets interesting, connecting a desktop computer through a wired link and we get on the internet with no problem so it's clearly down to the WiFi signal.
Switched off both modem and router for a few minutes and then swithed them on again and a short time later everything is up and running ok, so why this post ? Well I would be interested to know why the WiFi signal failed, could it be a sign that either the modem or router is on the way out ?
This has never happened before but I would be interested in comments anyone might have and in particular anyone who this has happened to before.
Tablets & Phone are in the same room as the router & modem and show a very strong signal

[#2]

@gleneagles
So you have a separate modem and router.
1. WiFi is only on the router, it has no connection to the modem so any WiFi issue is only to do with the router.
2. You have tested out a wired computer at the time the WiFi dies so you know that the router can connect to the internet, isolating the WiFi component of the router as at fault.
So good basic testing there.
Now some questions
1. What is the make and model of the router?
2. How old is it?
3. Does the router show a WiFi signal to the wireless devices when you cannot connect to the internet?
4. Can you log onto the router's admin page from a wireless device when you cannot get internet connectivity from said device?

[#3]

1. It's a Plusnet fibre router, I cannot see any specific model number on it.
2. Just under a year old
3. There is a green led on the router under the WiFi name and all other expected green leds are also on
4.At present I am unable to confirm that as everything is working at present. If the problem occurs again I will check that out.
Out of interest  I connected chromecast which failed to connect but has always worked ok in the past, could this have anything to do with the problem ?

[#4]

So the router isn't that old then. Given the always on nature of the router, they do fail but 12 months isn't too long.
I guess next time, you cannot connect via WiFi, the check to see if the admin page is still accessible may offer some hint.
I don't have a Plusnet FTTC router here so cannot offer any help in regards to the settings. Does the router admin pages give the firmware version? There maybe a new firmware version available.

[#5]

I was amazed to find numerous posts on the internet that chromecast can muck up your WiFi, never thought that could have been the cause but I am fairly convinced that is what happened.
Simply cannot understand how I have had no problems with chromecast in the past.