Testgate: The answered and unanswered questions from Mercedes & Pirelli's 'secret' test

Uncovering the furore which has overshadowed Nico Rosberg's win at the Monaco GP as the FIA accuse Pirelli and Mercedes of running an unauthorised test after the Spanish GP...

Who drove at the test?
This is another unknown - and the absence of any clarity perhaps suggests the answer will be critical in determining whether the test was, in effect, carried out by Pirelli or Mercedes. Could Lewis Hamilton or Nico Rosberg have taken part?
Hamilton has been quoted as telling reporters on Sunday night: "We were required to do some work and we did and it was good fun." It is an established fact the test took place between Wednesday May 15 and Friday May 17 - the week immediately after the Spanish GP - and Hamilton flew to America on the Monday. It is possible that he then flew back to Barcelona to take part on either the Thursday and/or the Friday - the test was extended to a third day due to rain. Was it a 'secret' test?
The answer - as you might expect - depends on who you listen to. Brawn is adamant it wasn't a secret - to quote the Mercedes boss: "While we were setting up to do the test, all the other teams were still there. Why didn't they see that our trucks weren't going home? There was no attempt to make it a secret test. It's up to Pirelli to inform people if they wish to. It's not our responsibility to advise people. There was no attempt to make it a secret." Red Bull's Christian Horner, on the other hand, described the test as "underhand", and neither Mercedes nor Pirelli acknowledged the test had taken place when they faced the press in Monaco prior to news of its existence breaking. And nobody spotted Mercedes testing for three days at Barcelona?
Seemingly not - which is rather remarkable given that the Circuit de Catalunya is an open facility and F1 cars make an awful lot of noise when in operation. Indeed, perhaps the most baffling aspect of this remarkably intricate and confused business is that news of the test only broke on Saturday night. Did anyone from the FIA oversee the test?
Another critical unknown. However, the stern line in the governing body's statement detailing that, following their briefing to Pirelli and Mercedes in early May about the terms under which a test could be conducted, 'the FIA received no further information about a possible test from Pirelli or from Mercedes-AMG' would seemingly indicate that no representatives from the FIA would have been present. What were the tyres tested at Barcelona?
A half-unknown. To quote Ross Brawn: "We didn't know that when you do a Pirelli tyre test that you don't know what tyres you are testing. You are given codes. Each day there was a batch tested and we still don't know what the conclusions were." Mercedes' rivals, however, are likely to be more vexed by Brawn's additional comment that "the majority of the tyres we ran were next year's tyres". 'Majority' is not 'all', and if even a small minority of the tyres run were the beefed-up compounds Pirelli are intent on introducing for the Canadian GP then the other teams will inevitably argue - with apparent good reason - Mercedes received an unfair advantage. "What's wrong is that a team, in an underhand way, consciously tested tyres that are designed for this year's championship," complained an angry Horner. How did the other teams find out about the test?
There was a telling clue in Sebastian Vettel's interview with Sky Sports News on Sunday night in which the World Champion described himself as "the second person" to learn of the test. It's unconfirmed at present,