"Rebekah Jenner writes from New Zealand to say that Auckland's Sky Tower and over a dozen other buildings will also be lit up when the baby is born," wrote one journalist on the blog.
"If the Shard is reading ... they're making you look bad here."
Initially it came to nought: "Bad news. The Shard will not be celebrating the royal birth ... Fine. Be like that."
Eventually the Shard offered free admission to the building to celebrate.
Monarchy New Zealand, who organised the illumination, agreed it got New Zealand a lot of attention in the world media.
"Free media coverage displaying some of our national landmarks is bound to be good for our image abroad and our tourism industry at home," said chairman Dr Sean Palmer.
Dr Palmer is encouraging people to donate to the Royal New Zealand Plunket Society.
"In 2011, prior to the wedding of Prince William and Catherine, the couple asked New Zealand well-wishers who wanted to give them a wedding present, to instead donate money to the Christchurch Earthquake Appeal," said Dr Palmer.
"We thought it would be appropriate to offer a similar gift to the new family and encourage others who were thinking of sending a gift to do the same."