Possible goof in Obsession

I have just seen the Obsession episode on ITV4 and noticed something interesting in the opening scene which is set in 1970. We see someone holding a partially torn newspaper and a front page story on it says something like "Kray brothers among 18 men arrested" which can be seen clearly by the viewer. The point I'm trying to make is that in 1970 as the Krays were by that time already serving life sentences for murder, is this a goof or can it be excused as artistic licence? (I know people can be arrested while in prison for other crimes, but I'm not sure if this ever actually happened in the case of the Krays.)