Iran's Ahmadinejad Announces Release of British Captives

Iran today abruptly announced the release of 14 men and one woman captured in disputed waters a week and a half ago. Britain did not concede they trespassed on Iranian waters. Tony Blair said the release was accomplished without confrontation or negotiation. Was there a deal or did Iran provide a surprise "gift" to the British people, as its president claimed? Was the US involved in a swap for Iranians held in Iraq?