i sent an email to London office and received a following response after one month.
Our records on this file indicate that the Step 1 assessment (sponsor's eligibility) was completed on 03-12-2012 by the Case Processing Center in Mississauga (CPC-M). As indicated on the CIC website, the processing times at the Visa Office are calculated from the date the Step 1 was completed. The current processing time in London is 68 months.
You can find more information on processing times on the following webpage: http://www.cic.gc.ca/english/information/times/perm/fc-parents.asp
While we understand the sponsor is anxious to be reunited with the sponsored family member, the application is well within posted processing time. There has been no undue delay in processing. This said, we endeavor to reduce the processing times and we are currently working on cases where the original application for sponsorship was submitted to CPC-M in 2007. The original application for sponsorship on this case was received at CPC-M on 09-06-2009.