Sienna Miller has sparked rumours she's engaged

In the photographs, obtained by MailOnline, the 'American Woman' star proudly flaunted her new piece of jewellery as she clutched onto her coat with her left hand in the Big Apple.

However, her hands were visibly bare last weekend when she walked the red carpet at the Golden Globes, held at The Beverly Hilton in Beverly Hills, California, on January 5.

Their engagement won't come as too much of a surprise to their friends as Sienna recently said she "loves" Lucas and she would be open to marrying him in the near future.

She said at the time: "It is love.

"It's nice and settled and happy. Yes, I would love to have more children. I would love a daughter as well. I think I would be open to getting married, yes."

The 'Alfie' star went public with her new relationship 12 months ago after she and art gallery owner were introduced to one another through mutual friends.

She said: "He's not an actor! He's not famous!"

Prior to this, the blonde beauty was in a relationship with Tom Sturridge - the father of her seven-year-old daughter Marlowe - from 2011 until 2015.

Meanwhile, Sienna previously said she wished she had her daughter Marlowe younger because she would like to have grandchildren "now."

She said: "I wish I'd had my daughter younger, and I could have grandchildren now. I'd like more children at my age now, too.

"There's something to be said for that dynamic. I was 30 when I had [my daughter]. It's a horrible facing of mortality. So, I'm all for young babies."