"In effect, it means we are in a full on war with Iran -- but nobody has officially declared it."

From [1] AFP, with thanks to Mackie:

Iranian Revolutionary Guard forces have been spotted by British troops crossing the border into southern Iraq, The Sun tabloid reported on Tuesday.

Britain's defence ministry would not confirm or deny the report, with a spokesman declining to comment on "intelligence matters".

An unidentified intelligence source told the tabloid: "It is an extremely alarming development and raises the stakes considerably. In effect, it means we are in a full on war with Iran -- but nobody has officially declared it."

"We have hard proof that the Iranian Revolutionary Guard Corps have crossed the border to attack us. It is very hard for us to strike back. All we can do is try to defend ourselves. We are badly on the back foot."