This section applies if—
a civil partner contributes in money or money’s worth to the improvement of real or personal property in which or in the proceeds of sale of which either or both of the civil partners has or have a beneficial interest, and
the contribution is of a substantial nature.
The contributing partner is to be treated as having acquired by virtue of the contribution a share or an enlarged share (as the case may be) in the beneficial interest of such an extent—
as may have been then agreed, or
in default of such agreement, as may seem in all the circumstances just to any court before which the question of the existence or extent of the beneficial interest of either of the civil partners arises (whether in proceedings between them or in any other proceedings).
Subsection (2) is subject to any agreement (express or implied) between the civil partners to the contrary.