Cara Delevingne wore a £300,000 necklace to her sister's wedding.

The supermodel was reportedly ''the butt of all jokes'' at Poppy's nuptials because of the pricey jewellery, which was given to her as a given at Cannes Film Festival last week.

A source said: ''Cara has been the butt of all jokes at the wedding because of the necklace.

''She has absolutely no idea how much the thing was worth and even turned up to the airport wearing it with a regular old tracksuit ... Apparently the sapphire is completely flawless and one of the best in the entire world.

''She has the price of a house hanging around her neck and she didn't even realise.''

Cara - who was delighted when the boss of Swiss jewellery de Grisogono agreed to let her keep the necklace - was at the wedding without her on/off girlfriend Michelle Rodriguez following speculation the pair could have broke up.

The insider told The Sun on Sunday newspaper: ''They've not properly split, but things really aren't looking good for them.

''Michelle was invited to Morocco but Cara told her not to bother coming along.

''She wanted to enjoy the day and couldn't be having to deal with her own relationship drama.''