Sir Paul McCartney has taken a stake in Magex, the digital commerce services company majority-owned by NatWest. His investment comes in addition to the $80m (&£54m) round of private equity funding Magex completed in April. Magex has also appointed a new chairman and chief executive – Patrick Campbell, formerly an executive at US online stock broker Ameritech. Campbell will spearhead Magex’s “rapid expansion” in the US. Magex clients include Universal Music Group.