LONDON—Planning permission for the largest addition to the British Museum in a century was expected to be a formality, until the Camden Council said no last month. The planning authority is now giving some details about its decision to reject the proposal, which called for a five-story building with three basement levels for a special exhibition gallery, conservation laboratories, offices, and collection storage rooms.

Among other concerns, the council says the large-scale development would be harmful to the listed buildings in the Bloomsbury Conservation Area and would detract from the area’s character and appearance. The council also cites concerns about “traffic disruption, sustainability, and biodiversity.” The museum says it’s considering its options, which include appealing the rejection or coming up with a new, smaller proposal.

Read more at the Guardian.