It is mentioned during the 1983 scenes that Gerry's baby daughter is Caitlin. In the 2006 episode "Ice Cream Wars", Caitlin had apparently just completed her A-levels and was considering a gap year before going to university. This would make her 18 or 19 in 2006, meaning she wasn't born until 1987/1988.
Gerry is seen chatting to a WPC who is quickly identified as "Sandra" in 1983. He is then warned off by Martin Ackroyd who says she is "Mr.Pullman's daughter". In several earlier episodes, it was established that Sandra Pullman's father committed suicide when she was 14, so such a warning would not only be irrelevant but hopelessly late.