Casino Royale (1967)

Question: At the beginning, M and agents representing the USA, Soviet Union and France try to convince James Bond to come out of retirement. Bond steadfastly refuses; whereupon, M lights his cigar as a signal for British troops in the distance to destroy Bond's estate with mortar fire (M is accidentally killed in the mortar attack). But what was the purpose of destroying Bond's estate? Wouldn't that action only drive Bond further away from rejoining the spy corps? Why would the British government go to such lengths to punish Bond? And then why did Bond return to the secret service, anyway, after such treachery?