Hi guys.
Just looked at my keyring given to me by my estate agent and it says
" This key is released to enable you to view the premises and for no other purpose. Its release does not imply any right to take occupation or to carry out any work to the property. Keys must be returned on the day of release unless otherwise agreed "
I had an electrician visit the property I’ve just bought. The estate agents didn’t want to show him around, so gave him a key to get in himself. I guess it is for this occasion, when estate agents cannot/don’t want to show people around. They either gave you the their spare key, or the key doesn’t matter anymore so you got it.