And that also !
Mad really, seeing as it was only in shot for a few seconds, I'm sure it could have easily been edited out later. It was quite obvious, so I'm not sure if it was a mistake, or whether it was deliberate.
Just thinking more about this, and I suppose it's fair to say that fictional tv programs and films are basically a cross between reality and fantasy. The story is usually made up (unless it's a true story or based on one), and the scenario is to some extent made up as well. With some tv and films, this is also going to have to extend to the scenery, props and locations etc unless it's got a multi million dollar Hollywood budget.
People filming something that's not set bang up to date in the present day are likely to have an element of difficulty in getting things totally accurate. The further back in time, the harder it is. For example, if you wanted to film a street scene that was set in 1984, where can you go that looks the part now, in 2012 ? The obvious giveaways are going to be things like satellite dishes, lottery signs in shops, big wheelie bins that didn't exist outside private homes in the 80s, cars, phone boxes, the list goes on. And of course, the lack of slam door trains. I know they still exist on heritage railways, but many have been repainted and are no longer in their 1980s BR liveries.