In James v Thomas  EWCA Civ 1212, the Court of Appeal fine-tuned some points on constructive trust and proprietary estoppel, with reference to shares in property. To note from Sir John Chadwick’s main judgment:
A constructive trust can arise some years after the purchase of the property by the sole title holder alone. There is no requirement for the claimed beneficial interest to arise at the time of purchase. However, in this situation, without an express post-acquisition agreement, the Court will be slow to to infer an agreement from conduct alone.
Contribution to mortgage capital repayment per se is not necessarily enough to infer agreement to a beneficial interest.
It is not necessary for a specified share or part of the property to be mentioned in an assertion that a beneficial interest in the property would be given by the defendant to the claimant. It is sufficient that the property at issue is identifiable, pace Lissimore v Downing  2 FLR 308.
The judgment is also worth reading when considering what kinds of acts and statements, in what kind of context, will not give rise to a constructive trust or an estoppel.