Rats

[Joe]

So a quick update, it appears there was not a hole on the outside of the property, instead the rat got into the house when the back door was left lying open. It then hid for weeks (at least) and built up a food supply and at the same time it had chewed through a wall and into the cavity.
The issue appears to be resolved now, it was trapped in the cavity and poison was pushed through and it died about three days later.
Tomorrow I will be removing the temporary block into the cavity and cementing it up. I suspect in a week or so the smell will hit for a few weeks but I didn't have many options at the time.
My big concern was a large family of rats with the potential to increase to hundreds.
The down side was having to kill the rats, I had started to like it over the last week when it had out smarted me every time and if I had known it was only one rat I would have trapped it and let it go in a far off forest. I'm not sure if every rat was as smart as this one but it was probably the most intelligent animal I have came across.
If anyone ends up with this issue then don't mess around, take the kitchen apart, remove the cupboards if required and track it down. You won't trap it or poison it as it will has food hidden everywhere. You even need to check inside Washing Machines,Freezers etc. incase it's hidding inside or has chewed electrical wiring.
Once the hidden food is found you might have half a chance.