Invest NI's chief executive takes the oath and settles into the witness chair.
He's been in his role with Invest NI since 2009 and spent time shortly before that as a DUP adviser at Stormont to the then first minister Ian Paisley.
Invest NI is an non-departmental public body that was set up to help Northern Ireland's economic development.
Its parent department is Stormont's Department for the Economy - formerly the Department for Enterprise, Trade and Investment (DETI), which ran the RHI scheme.
The inquiry's junior counsel Donal Lunny tells Mr Hamilton that he'll be questioned about whether Invest NI missed an opportunity to tell DETI about some of the flaws in the energy scheme.