What to wear when the King and Queen of Englandcome for a visit?

Robbins worked very closely with John Bright from London-based Cosprop, which specializes in historical finery.

She accessorized it with a tiara made with Swarovski crystals.

DOWNTON ABBEY

Jason Bell/Focus Features

The whole thing came together beautifully, says Robbins.

Cora wears this shape really, really well.

In other words: yass, queen.

DOWNTON ABBEY

Courtesy of Anna Robbins

Downton Abbeyopens in theaters on Sept. 20.