To contrast the attitudes of the US Congress and the British Parliament, start with Iran. Today, the palpable welcome by MPs for Tehran’s suspension of high-level uranium enrichment was matched only by anxiety about the UN excluding Iran from the Syria talks that start today in Switzerland.

The unease emanated not only in Labour but on the government benches. John Baron, who pressed William Hague for early “normalisation” of UK-Iran diplomatic relations after an “encouraging start” to nuclear negotiations, is his own man. But he was backed by fellow Tory Phillip Lee who deplored the “overnight debacle” of the cancelled invitation and wanted “a Gorbachev-like” approach to “reform-minded Iranian politicians”.

Many MPs, in other words, want to go further, faster in rapprochement, with Iran. Contrast that with Congress, where many members have been pressing for sanctions to be tightened. All of this makes it hard not to conclude that one difference is the much greater power wielded by the Israel lobby in the US legislature than in its British counterpart.

All of this, as new photographic evidence – dubbed “compelling and horrific” by Hague and “deeply disturbing” by his Labour counterpart Douglas Alexander – suggested that around 11,000 detainees had been systematically killed by a Syrian regime hitherto backed by Iran. Conservative Robert Halfon was more neocon in tone, simply asking Hague how he was going to “stop” the influence in Syria of Iran – “the Soviet Union of the Middle East”. Hague’s reply was modulated. While Iran should stop supporting “the brutality of the Assad regime”, it is “in Iran’s interests for there to be peace in Syria. We therefore ask Iran to embrace that opportunity”.

Hague stuck doggedly with the US/Syrian opposition line that it was right to withhold Tehran’s ticket to the Geneva II talks without a “more public and constructive” commitment to a “transitional” Syrian government. But he “absolutely” agreed with Jack Straw – 13 years ago the first foreign secretary since the 1979 revolution to visit Iran – that Tehran had been “badly burned” by the thwarting “by forces inside the US” of their “best efforts” at rapprochement ten years ago, and this shouldn’t happen again.

There was little light relief. While arguing that only the EU could conserve marine stocks, Labour’s Ben Bradshaw announced that “fish swim around and are no respecters of national boundaries”. Hague replied that “the observation that fish swim around is not among the most devastating revelations to be heard in the Commons recently, but we know the point the right honourable gentleman is making.” Master of the mild put-down that he is, he almost managed not to sound patronising.