New job during notice period

[M2AL]

Hi everyone can any body give me some advice.
So I’m currently on maternity leave , unpaid just extended to twelve months . I handed my notice in at my job in an office however I didn’t state how many weeks notice as I wouldn’t have been returning to work till the start of feb with the company any way . However my new job have put my start date four weeks after the day I handed my notice in at my old job. Now I understand that my notice is six weeks but can I start my new job after four weeks considering I don’t actually go to work/ wouldn’t have been returning until feb any way and they are not paying me maternity pay . Would they know I’ve started the new job. Or is it something to do with taxes etc why it would be easier to wait the other two weeks.

Thanks in advance

Not an expert but I think you'd need to ask your current employer if they can release you from notice earlier? I don't expect it'll make much difference to them either way if they're not paying you anyway? Might be some impact on accrued leave though.

@HowFastIsTooFast
Thanks for your answer . I’ve tried emailing on numerous occasions but my workplace are not getting back in touch with me