party wall agreement surveyor question

[ChilliChoco]

Our neighbours are having a loft extension done (semi detached to us). They have appointed a surveyor. We are happy for only one as I spoke to him and he seemed good and would share information about progress with us.
However, I wasn't expecting that he would need to go into our loft.
Is that the norm? I thought he would be able to just see how things are going on from our neighbours' side.
Any surveyors here or anyone had this done?

We are going through this now. Our neighbours are having an extension.

The surveyor basically came to our house and inspected and photographed the party wall our side. He explained that they need to record the state prior to works so that if the building work affects our side (cracks/subsidence etc) our next door neighbours will be liable to pay to rectify damage.

Thank you @Elzbells

H is a surveyor. Yes he'd need to see your side, it's to protect you and your building.