I have been considering the case of Walsh v Singh & Anor  EWHC 3219 (Ch). I don't think that it decides anything new, but I would still recommend that it be read, as it seems to me to be a classic application of the (current) property rules relating to cohabitees.
The parties began cohabiting in 1997. In April 1999 a property was purchased in Mr Singh's sole name. Miss Walsh claimed a 50% beneficial interest (or some other share) in the property under a constructive trust or proprietary estoppel. She did not contribute financially to the purchase price of the property, but said she was promised a half share.
Miss Walsh did make a significant contribution towards the development of the property, and loaned certain sums to Mr Singh. The judge held that her contributions would be sufficient to give rise to a constructive trust or estoppel if the necessary common intention coupled with detrimental reliance existed, or the necessary belief (similarly coupled) in a shared or joint beneficial interest was both held by Miss Walsh and encouraged by Mr Singh. However, he was unable to accept Miss Walsh's evidence that she was promised or that she was encouraged to believe (or did believe) that she would have a 50/50 or indeed any other share in the property at the time of its purchase, or subsequently.
The parties had become engaged in April 2001. The judge found that they stayed engaged until late 2005, and that the engagement ring remained Miss Walsh's throughout, and is still hers, despite her returning it to Mr Singh for resizing.
In the circumstances, Miss Walsh's claim against the property was dismissed, although she was entitled to the repayment of the loans (with interest), and to the return of the engagement ring.