Maltawildplants.com is now considered an online flora of the Maltese islands, portraying more than 900 species of plants found in Maltese habitats. It harbours a forum created in 2005 were memberes discuss topics about the Maltese flora and ID of plants.
I haven't time to delve deep into this but from Haslam, R. pulcher would fit. Additionally, 'obtusifolius' means wide leaf and using visual logic, (not botanical evaluation) the leavs do not look very wide. We wait the experts...
I have found a plant like yours but the teeth were less than 1mm while yours look longer... do you confirm? Saying so becasue flora europae divides two bulky groups of Rumex from the length of the teeth of the valves.
My specimen is also under investigation, but on the first round it is neither R.pulcher nor R.obtusifolius