Citi Financial Request of overseas payment for purported sweeptakes win of $ 50,000. Clearwater Florida

 Citi Financial, a "Financial Express Company" sent me a letter- the envelope comes from England with no return address- stating that I won $ 50,000. They sent a check for $ 2,400 supposedely issued by the " Mercury Insurance Group" [no way to know whether the Mercury Insurance Group has anything to do with it or not] and asking to contact their phone number. The payment is supposedely part of a $ 50,000 won in "consumer promotion draw". They ask to deposit the check, then send them a $ 980 "tax clearance fee" that non residents are supposed to pay, as the draw took place in the UK.  The funny thing- the letter is signed by a "Mrs. Elizabeth James", but the signature reads something like "N. T. Anant" , and the same signature is on the check. I saw another report of the same scam on ripoff report- I am not sure what to do with the fake check. If the Mercury Insurance Group is not involved, this is something they should know. On the other hand, I have no way to know what is going on.