Possible ESA fraud?

zzzLazyDaisy

Presumably if the flap came open that easily, it can just as easily be stuck down again. In any event, the offence is opening a packet intending to act to the person's detriment and without reasonable excuse. There is no suggestion here that OP is intending to act to the person's detriment - and even if she has, it is not very likely that the police are going to be very interested, even if the DWP report their concern that she might have opened the letter, which really is not very likely.

POstal services act 2000, S84 Interfering with the mail: general.
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(3)A person commits an offence if, intending to act to a person’s detriment and without reasonable excuse, he opens a postal packet which he knows or reasonably suspects has been incorrectly delivered to him.
(4)Subsections (2) and (3) of section 83 (so far as they relate to the opening of postal packets) apply to subsection (3) above as they apply to subsection (1) of that section.
(5)A person who commits an offence under subsection (1) or (3) shall be liable on summary conviction to a fine not exceeding level 5 on the standard scale or to imprisonment for a term not exceeding six months or to both.