St Tugual's Chapel dates back to the 11th century when the island was a haven for an order of Norman monks. However, there is evidence that the site has had religious significance since the 6th century. The chapel was designed in such a way that they could sit in the building's north nave without being seen by the public who would sit in the west portion of the chapel.
In the years before the Wood family took hold of the lease on the island, in 1949, the grounds around the west and south of the chapel had become overgrown and it was in their time that the churchyard come garden was made around the church.
References:The Clementinum is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic.
Its history dates from the existence of a chapel dedicated to Saint Clement in the 11th century. A Dominican monastery was founded in the medieval period, which was transformed in 1556 to a Jesuit college. In 1622 the Jesuits transferred the library of Charles University to the Klementinum, and the college was merged with the University in 1654. The Jesuits remained until 1773, when the Klementinum was established as an observatory, library, and university by the Empress Maria Theresa of Austria.