2A drain - brand new battery keeps going flat

[zippy_6]

Problem as above: battery fails to hold charge.

The timeline is:

• dash indicator started to flash low key battery
• some weeks later (yeah  ) changed the battery of the key fob, which is when it started to kick off
• couple of days after changing the battery, went to get in the car and couldn't unlock, couldn't start the car after manually unlocking it
• called out the RAC - patrol diagnosed a flat battery (alternator fine), charged it up and then was left running for a good hour if not more
• next day, battery flat again, called out RAC again and patrol recommended changing the entire battery with an EFB Varta battery
• following day, same story - flat battery! This time, the patrol found a steady drain of 2A on the battery, but obviously he wasn't going to hang around finding the source of the drain; instead, he recommended calling out an auto diagnostic company rather than going to Mazda (generalists)
• called out https://airbagman.co.uk/ who failed to find a fault but sent another colleague to look at it who couldn't find anything either and recommended yet another auto electrician

At this point, I've given up and booked the car in with Mazda, but it feels like a needle in a haystack problem so I'm posting here to see if anyone else has experienced a similar issue.

[zippy_6]

Sorry, should have said, it's a 2013 Mazda 6 2.2 SE-L Nav Manual Diesel with Start/Stop