The development included them adding a separate male and female dressing room linked to the main bedroom.
They also opted for a nursery to take care of their growing family and air conditioning throughout.
The nursery, which will be once again in use for the new baby, is reportedly a luxurious space with views of the exclusive neighbourhood of Chelsea.
Pippa and James had to move out for the major changes to take place, but they moved back in in 2018.
READ MORE: Pippa Middleton’s mansion has £1m nursery for new baby
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