Please provide a detailed answer for this.

Marcus owned the 99-year lease on a flat, title to which was registered. The flat has a kitchen, living room, bathroom and two bedrooms, one of which is very small. In May 2018 Marcus was posted to New York for five years by his employers. Not wanting to sell the flat, or leave it empty, Marcus agreed that his best friend Jason could live there with his girlfriend Phoebe and Phoebe's six year old son, Tristan. Jason and Phoebe signed identical agreements with Marcus. The agreements were made by deed. Phoebe actually signed the day after Jason because a road accident meant she missed her appointment with Marcus' solicitors. The agreements were described as a licence. They gave the right to reside in the property for five years, unless Marcus returned from New York earlier. Jason and Phoebe each agreed to pay 300 per month. Marcus reserved the right for him or his agent to enter at all reasonable times to inspect the state of repair of the property and the right to put in other occupiers. He retained a set of keys to the property. Marcus has decided to remain in New York. He has sold the 99-year lease to Karl, "subject to Jason and Phoebe's rights, if any". Karl is insisting that Jason, Phoebe and Tristan leave. Advise Jason and Phoebe.