How does Tesco's removing Unilever brands from their shelves impact their supply chain?

With the news that Tesco, the UK's largest supermarket chain has removed Unilever brands from their online site and are threatening to remove Unilever brands such as Marmite, Ben & Jerry's, PG Tips and Pot Noodles. How will it impact their supply chain? Who holds the power? The UK's largest supermarket grocery buyer or Unilever the UK's biggest food and grocery supplier.