Well, you did ask........
The relevant statutory instrument is The Social Security (Maternity Allowance) Regulations 1987
The relevant section says:
Disqualification for the receipt of a maternity allowance
2.?(1) A woman shall be disqualified for receiving a maternity allowance if ?
(a) during the maternity allowance period she does any work in employment as an employed or self-employed earner, and the disqualification shall be for such part of the maternity allowance period (but for not less than the number of days on which she so worked) as may be reasonable in the circumstances;
So it seems to me that you definitely cannot receive MA for the period you actually work (which is fair enough). But your disqualification is only for a period that is "reasonable in all the circumstances".
In my case I lost three months of MA for doing two days of work, which seems to me longer than a reasonable period.
On the question of whether anyone would have found out, I guess it would depend on how you do your invoicing/ handle your tax and stuff. There would be some risk of being found out, but it might be quite low. On the other hand, the effect of being found out could be quite serious if it was thought that you had done it deliberately.dishonestly. For me, just after I had had ds I wasn't really in a mood to take any sort of risks, or add to my stress level. I think I will do the same with my next mat leave which will start in January, but hope that I won't have to do any work in the first six months.
Bit of an essay - sorry.