It's an Alstroemeria, one of the hybrids - as to which, I've no idea, there are so many.

Thanks Bamboo,your just great.

I am pretty sure that this one is Alstoemeria " Pink Blush"

Telling us the height of the plant would narrow our guesses down a lot.

It could maybe be Pink Blush but it also looks a bit like Inticancha White Pink Heart to me.
Inticancha White Pink Blush and Inticancha White Pink Heart aren't 4 years old though, 2 at the most.

There are loads of different types of Alstroemeria and a lot of them very very similar.

On reflection, i'm changing my mind about the Inticancha's, they don't have the yellow splashes.

Yes Louise1, this is the fourth summer I have it. I Keep it in a glasshouse for the winter and is in the same pot and compost.I feed with potash,I don't know if that is right or wrong,but it seems to work. At the moment it is 8" high from the top of the compost.

Is yours an area that gets abnormally cold winters ?
If not put it outside - they're much hardier than everyone thinks and will survive a minus 12 winter easily.

If you're worried about it though, mulch it before the cold temps set in.

I have quite a number of them here and i leave them uncovered all winter, a grower i know further north also leaves them outside over winter and always tells customers that they'll be fine outside in low temps.