I don't know whether it was the first delivery or not Micky, but Joe Baugher has this comment:
61599 Delivered to USAAF 20Apr45 Assigned to 324th Army Air Force Base Unit, Chatham AAF, GA To RAF as Washington B.1 WF434 Mar 22, 1950. Assigned to Washington Conversion Unit, RAF Marham; code FB-K To 23 Maintenance Unit, Aldergrove, Northern Island for storage. Scrapped 5Jul56 To Proof and Experimental Establishment, Foulness May 8, 1957 for use as a target and ordnance testing Sold as scrap Aug 8, 1957.
Also note that WF434 was the first RAF Washington serial allocated.
According to our own Washington File it was actually WF437 which landed first in UK on 22.3.1950 It was part of a four aircraft delivery but experienced engine trouble and had to land prematurely at Marham. So if that is what counts 44-69680 (WF437) was the first....
PS: It is of course quite possible 44-69680 in fact should have been the first to land anyway. No idea how the actual plan was since the other three rapidly followed suit.