About the border of Iran / Iraq.
When the western nations England and France created this artificial thing called Iraq they defined that the river between Iran and Iraq is 100% iraqui territory.
After WW2 the imperial Iran was an ally of the USA - so the Shah as an US-puppet feeled strong enough to start a campaign to make the middle of the river the new border.
For Iran this river is important because one of the most important oil cities - Abadan - is reached by this river.
The Shah supported the iraqui kurds with heavy weapons and also with retreat zones to regroup on iranian territory.
Iraq was not able to win against these kurds - and so there was an official treaty where Iran and Iraq agreed that the middle of the river was the border between both countries. If I am right it was called treaty of Algier - but I am not sure about this.
The important thing on this treaty was the inofficial part: Iran stopped immedeately any support for the kurds - and as often in their history the kurds were betrayed and lost against the Iraquis.
Later Saddam (at this time a friend of the US

) revoked the treaty and started the Iran-Iraq-War.
After the Iran-Iraq-War this question was not solved.
But before the Desert Storm Saddam tried to get iran as an ally and accepted officially the middle of the river as the border between Iran and Iraq. This idiot really believed that Iran would support him and sent during the war 150 of his fighters to Iran (which he never got back).
Back to the today news:
So - some british soldiers have entered iranian territory and were arrested. **** happens - and its good that they were captured unhurt.
And I dont think that they will be taken to a infamous prison where they are tortured or forced to perform homosexual practices while stupidly smiling soldiers take thumbs-up-pictures from their comrades.
This thing will be solved in typical british-iranian diplomacy:
GB will pay some corrupt fat mullahs money and the british soldiers will be released with their equipment within some hours.