Trying to persuade boss into flexible working after mat leave

[ScottishElle]

how do I persuade my boss into letting me go P/T after baby?

initially i asked informally and was told, was told:
we need your senior job full time (non direct sex discrimination)
you would lose annual leave (disadvantage due to being on mat leave)
maybe it wont suit you coming back (great, thanks!!)
now i have applied formally, i need to get some smart answers for what feels like an interview for my own job

any tips or suggestions would be great, im confident i can do it, and i really want to show that i can still add value to the business...and i dont want to scream/cry at the negative stuff im getting told...

[givemeaclue]

Are you following the legal request process? If not , submit your written formaof start this. I asked for a trial period, they may agree to that -3 months trial then review?

[flowery]

You persuade him by demonstrating that either you reducing your hours will have no negative effect on the business, or ideally that it will have a positive effect.

What do you think his concerns will be?
How much of a reduction do you want?
Why do you think this is possible - how do you propose to get the job done in less hours?