Pastor Patrik Goransson of St. Michael's Church in Tallinn told regional newspaper Harju Elu that an invitation for members of the royal house to attend the event had already been sent a couple of years ago, for the simple reason that King Carl XVI Gustaf, the Crown Princesses' father, has long supported the restoration of the chapel.

"The windows, for instance, were restored with the help of a royal donation," the Pastor said.

St. Michael's Church (Rootsi-Mihkli kirik in Estonian) is the home of the Swedish Lutheran congregation in Tallinn, and as such indicates the strong historical link between Estonia and Sweden; Estonia came under Swedish rule in the century and a half from the mid-16th to early-18th centuries, and significant populations of Swedish speakers, especially in coastal areas, including Naissaar, continued to live in Estonia down to World War Two.

Setting up the visit

The first invitation was handed to the royal house during a visit of a delegation of Estonian Swedes to the royal castle at Stockholm in 2016. A formal invitation signed by the head of the Estonian Evangelical Lutheran Church, Archbishop Urmas Viilma, followed.

"Crown Princess Victoria has visited Lithuania and Latvia on their centennial this years. The visit in August will thus form a part of the events of the centennial of Estonia," Goransson said.

He also noted that the Swedish ambassador to Estonia, Anders Ljunggren, had been instrumental in laying the groundwork for the visit.

Naissaar island, at 18.6 sq km in area, dominates the approaches to Tallinn bay, and was off-limits to the local populace throughout the Soviet era, when a large naval mine factory was built there. Post-restoration of Estonian independence, it has been designated a nature reserve and has a negligible permanent population.

The chapel being restored was first consecrated 80 years ago, on 11 September 1938. The wooden structure was built to a design by Estonian architect Karl Tarvas.

The Crown Princess and her husband were last on an official visit to Estonia in 2014. The visit is at least the third European Royal visit to Estonia this year.