Iñaki Urdangarin, 51, was jailed in June 2018 after being found guilty of fraud, tax evasion and embezzlement in a high profile scandal that rocked the royal family.

He was accused in Mallorca of using his royal status to win contracts and was found guilty of embezzling €6 million of public funds through his not-for-profit Noos Institute.

His sentence was reduced from six years and three months to five years and ten months after an appeal and he was sent to serve time in a private wing of a women’s prison near Avila.

But on Thursday he began the start of a 16 hour release from behind bars, a privilege granted by a court in Castilla y León to avoid him suffering “absolute isolation”.

Urdangarin, who is married to the Infanta Cristina, the younger sister of the Spanish monarch with whom he has four children, will spend two eight hour days performing voluntary work at an adult community centre before returning to the prison at night.

He spent his first day helping out at Hogar Don Orione, a centre for adults with learning difficulties, in Pozuelo de Alarcón, where he smiled at the cameras and waved as he entered the building.

Granting permission for his day release, the judge said: “Carrying out an activity outside [prison] is positive to reduce or eliminate social exclusion or dehumanisation, the destruction of the individual which living in absolute isolation can bring.”

But some said the decision to grant the former Olympic handball champion such a privilege reeked of special treatment.

“When we talk about Urdangarin and other people in the public eye we can see that the justice ministry does not treat all equally,” said Yolanda Díaz, an MP for Podemos.

Others were quick to compare Urdangarin’s privilege with the treatment of those Catalan separatist leaders who have already been behind bars for almost two years without being convicted.

“Urdangarín, leaves prison in an official car and escort, to the door of the Center. The Political Prisoners, moved from one place to another, in a van that looks like a TANK and handcuffed as if they were TERRORISTS? … No way …”

READ MORE: 

• Iñaki Urdangarin chooses women's prison to serve his time 
• Behind bars: King's brother-in-law jailed over graft scandal
• Spanish king's brother-in-law: From Olympic glory to royal shame