I never thought of this scenario

I decided on a quiet breezy Sunday morning, to upgrade my routers firmware. Which required  a router reboot.
So it lost all its DHCP tables.
However apart from 10 seconds of internet outage, the rest of the network carried on nicely (nothing uses the router's wifi, as it's in a remote space).
I then restarted a piece of kit I am working on, and it popped up in the first available DHCP slot.
My question is, if that had already been occupied by another piece of kit, would I have ended up with an IP address clash?
It seems to me that checking for conflicts only happens at lease start or lease renewal times?
Or does that imply that the router did check the ip address first before allocating the IP?
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Canada is all right really, though not for the whole weekend.
"Saki"