Both of Guthrie's goals come from free-kicks - the first unintended, as it flew through a packed Birmingham penalty area, and the second an accurate set-piece that found the net via a post.
Those goals helped Reading make it 13 points from their last five league games and leave Birmingham unable to cap a memorable week with a third successive victory.
Lee Clark's men beat Sheffield Wednesday 4-1 in the league last time out and then followed that up with a 3-1 cup win over Swansea, and buoyed by those successes they started brightly.
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Thames Valley Police named the victims as Savaan Mundae, Jaspal Bahra, Thanh Nguyen and Captain Michael Green.
The latest attack on him, from a plugged-in Tory MP, is for his “reluctance/refusal to hand over the money to Iran to free Nazanin”.
Early forecast for the west of the region