Here's what the UK requirements are now (out of MATS Part 1)
9 ATC Watch Log
9.1 An ATC Watch Log detailing significant events and operational information of note to controllers and unit management shall be maintained by each air traffic control unit.
9.2 Whatever the format used to maintain the ATC Watch Log, it shall include the name of the ATC unit and the period for which the log contains entries and shall be capable of providing a documentary record of entries made.
9.3 An ATC Watch Log shall permit descriptive text associated with a particular date and time (in UTC) to be recorded and enable the identity of the author to be established. Entries shall be made in chronological order and, as far as possible, concurrently with the events being recorded and should be of sufficient detail to enable subsequent investigation of events to have a complete understanding of actions taken by ATC.
9.4 Items logged shall include:
- changes to the serviceability of radio and radar aids;
- essential aerodrome information and changes to runway in use (at aerodrome based units);
- result of routine equipment checks conducted by controllers;
- details of reportable events such as aircraft accidents, incidents and AIRPROXs;
- any unusual occurrences;
- handover of responsibility for providing ATC services and, at units not operating throughout the 24-hour period, times of opening and closing of watch.
9.5 An ATC Watch Log shall normally be maintained in each control room or in association with each operational control position. When approved by the CAA, and where a suitable unit management structure exists, a single Watch Log may be maintained in respect of more than one control room or operational position.
9.6 Measures shall be taken to ensure that entries made in an ATC Watch Log cannot subsequently be altered or in any other way be tampered with.
9.7 The method by which the ATC Watch Log is managed and entries made shall be detailed in MATS Part 2.
Seems to work OK.
Goldfish, I'm not sure why the ATC log is considered to be any more 'legal' than any other document that might get pulled out in court or wherever sometime. As far as I'm aware it doesn't have any particular or special status in the UK. Certainly it doesn't seem any more important in reconstructing events than the strips and many units now use electronic strips.