It's an oxalis - variety depends on the flower, but it might be Bermuda buttercup (Oxalis pes-caprae)

Oxalis. I have grown to love them.

dig the root our as much as possible and dont allow it to flower. the pods are 'explosive ' and throw seed about 1m away. re move seedlings as soon as they appear.

Steve - I'm sad to see that. The Bomerea is a lovely plant and well worth saving. Mine is romping away.

Probably Oxalis corniculata--a terrible weed in greenhouses.

I find O.corniculata is smaller than this plant seems to be, and its leaves go a burgundy colour.

Steve - I've just taken a proper look at the photo, and I can see two plants in there neither of which is a Bomarea. Not sure what the one with the strappy leaves is either though.

Meanie
This is not the Bomarea but a Bromeliad a Puya berteroniana to be exact my first senior moment I think or too much fosters this plant is only very young and will get very large maybe 6ft plus in a pot have a look
http://www.strangewonderfulthings.com/150.htm
I do have have a very young bomarea that has take me 6 months to germinate and is about 2 inch high did yours take a long time to germinate
Steve

That's cleared up then!!
That's a great Puya too - I lack the patience for that.
The Bomarea started germinating after four weeks. Two months on the fifth one has germinated. The first one stands about 60cm now with a total of four stems growing.

Hmm...I think that Beattie may be right. It was a little hard for me to tell the scale. The flower buds seem a little on the small side--relative to the leaves--and too solitary, and the stems seem somewhat thin, too, though.

You could lift it from the pot and with the root ball being plunged in and out of a bowl of tepid water gently tease the two plants apart. Just a thought.