Some what ifs......
1 The phone was taken to the terminal building and had then blown up?
Hero pilot saves hundreds of lives as a headline?
2 phone is found to be ... Just a phone but capt claims he believed it to be a bomb, broke the law to protect lives! EU JAR and ANO allow for this.
3 The airline put capt and f/o through a CRM refresher concentrating on DM and one of the curved balls addressed was ,yes you guessed it Finding a mobile phone on board after push back.
4 The LGW chief pilot , training manager and tech manager are all good blokes?
Actually 3 and 4 aren't what ifs .
If the capt can prove he believed it could have been a bomb and that the average pilot with his training and experience may have made the same
decision , he should get away with it , IMHO see 2 and 3 above.
Mind you he may get done for littering or if the phones damaged criminal damage.