UK officers, together with Transport Secretary Grant Shapps, boarded the vessel at Canary Wharf in east London on Tuesday.
The title of the vessel's proprietor was not made public.
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The 58.5-metre yacht is vivid blue and options an "infinite wine cellar" and freshwater swimming pool, based on the Nationwide Crime Company.
It's valued at $24 million.
The Phi, named after a mathematical idea, was in London for a "refit" however "will not be going anyplace," Mr Shapps stated.
The yacht is registered in St. Kitts and Nevis however carried Maltese flags to cover its origins, the crime company stated.
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