Monaco's Princess Charlene attended a two-day celebration to mark St Devote's Day, a national holiday honouring Monaco's patron saint. Accompanied by her husband, Prince Albert II, Charlene took part in the traditional boat burning festival on the first day and in the cathedral service on day two.

The mother of twins wore an all-navy ensemble to attend the religious festivities at Monaco cathedral on 27 January. She donned a navy tailored coat dress and a scarf. Charlene paired her knee-length dress with blue over-the-knee boots and completed her monochromatic look by wearing scarlet lipstick.

Legend has it that Devote was a young Christian from Corsica who was martyred by the Romans during the persecution of Christians in the fourth century. Her remains were placed in a boat that drifted into the port of Monaco. It is believed that she helped Monaco in times of peril.

"The celebrations of the saint Devote are one of the oldest traditions of Monaco. Saint Devote is the patron and protector of the royal family and the principality [of Monaco]," a palace statement said.

St Devote's Day celebrations began on 26 January with the 38-year-old princess taking part in setting off a fishing boat at Port Hercule. The boat symbolises the arrival of Devote in Monaco. The annual tradition dates back to 1924 to the reign of Prince Louis II, the palace said.

The former South African Olympic swimmer graced the ceremony in a chic grey dress which she teamed with a poncho-style coat, grey scarf, cream gloves and suede knee boots.

Charlene's engagement followed her recent visit to the Vatican where she and Prince Albert II met Pope Francis. She attended an audience with the pontiff wearing a white dress and white mantilla, a privilege given only to seven royal women around the world.

Princess Charlene
Charlene wore a cream coat over a grey dress to the boat burning ceremony Getty Images