Nasheed, 48, arrived last night in Colombo and will be leaving by a Srilankan Airlines direct flight to London later today, Maldivian Democratic Party (MDP) sources said.
He is currently lodged at a five star hotel in Colombo and is expected to leave for London for a back surgery.
Nasheed was supposed to leave on Sunday after a deal brokered by diplomats from India and Sri Lanka as well as Britain, but his departure was delayed as the government imposed new conditions on his trip.
Nasheed initially refused the government request to leave a family member behind who had to sign as a guarantor for his return, but finally agreed to the offer.
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According to Maldivian government, Nasheed had signed an undertaking to return after his treatment and his brother has agreed to act as guarantor.
Nasheed, the country's first democratically elected leader, was sentenced to 13 years in jail in March over the arbitrary arrest of chief criminal judge Abdullah Muhammed during his presidency.
Nasheed resigned as the Maldives leader in February 2012 after weeks of protests over the judges arrest on corruption allegations.
The former president had appealed his prison sentence after backtracking on his earlier decision and opted to go to the Supreme Court instead.
In his appeal, Nasheed had sought a lesser penalty under the new penal code that came into effect in November. The Supreme Court had also been asked to nullify the charges lodged against him in the lower court and the subsequent sentence.
The current President Abdulla Yameen was elected in controversial polls in 2013 and is the half-brother of Gayoom.