Apparently Winslet had become 'increasingly frustrated' with Mendes's 'closeness' to Rebecca Hall. The director had recently cast the 'Vicky Cristina Barcelona' actress in two of his theatre projects (i.e definitely doing it) in London and New York.

A source apparently close to Winslet said:

"When Kate found out that Sam had grown close to Rebecca she was upset. Rebecca is totally Sam's type  -  a thespian mix of brains and beauty."

Someone shoot that source, please.

Meanwhile, Winslet is apparently being comforted by Leonardo DiCaprio (because they starred as lovers in two films) despite the fact that she is now in Mexico being comforted by Emma Thompson (literally this time, they're not lezzing up - as far as we're aware, anyway).

Another source, less pompous than the first one, said:

"Since Kate's marriage started to go south, around the time they were filming Revolutionary Road, they've [DiCaprio and Winslet] got closer again. Kate has always really adored Leo and feels like she can tell him anything.

"They were thrust into stardom together and were the only people who knew what the other was going through. He's been a rock for her."

Before finally adding:

"Leo and Kate have been like brother and sister."

Which is probably just one of the reasons that they haven't been shagging...