1659 Heavy Conversion Unit was based at RAF Station Topcliffe (located in North Yorkshire (approx. 35 km or 20 miles NW of the City of York) post May '43 until disbandment in September of '45.  It was originally one of the Canadian No. 6 Group HCUs but post Nov. of '44 fell under the control of RAF Bomber Command's No. 7 (Training) Group.  During the period requested, to the best of my knowledge, it operated the Halifax III and the assigned codes were FD & RV.  Earlier it employed Mk II & V Halifax and had been based out of the aerodrome at RAF Leeming.

If there is some specific info you require or are interested in just clarify and I'm sure there are great sources available to assist you in gaining more partuiculars. 

Speaking of HCU's ...

I'm curious if anywhere, anyone has any shareable pictures or photos of RAF Bottesford No. 1668 HCU around  the period of May-June1945?  While stationed there my Dad's crew flew in Lancasters coded J9 A, F, G, J & R and also 2K-M.  Unfortunately I don't have the individual serials for these aircraft but I believe they were all Mk IIIs.

Also they had as instructors a F/O Walker and Flt Lt. Leeder about whom there may be information available.

Of course if this query leads to successful results I'll try the same for the Halifaxes they flew from 1663 HCU, too!

Much appreciated.

Yes I would. Dad's crew were on Course 22B May 24-June 19/45 at 1668 HCU. It would be very interesting to compare logs. If you wouldn't mind sharing. My email is roful at sympatico dot ca (replace the at & the dot with the usual). Thanking you in advance. 

This is all very interesting for me - my late Dad (who died in 1998) was at Toppcliffe as part of HCU 1659. I have copies of his log book confirming this and all of his flights with F/O Bolt whose funeral was last Agust in New Zealand. I would like to hear from anyone with any connections to this. Mark