Don't know if they're Brits or not, but Roger Windsor, the chief executive of the NUM was later suspected of being a spy as documents that crossed his desk were regularly passed on to the police and Tim Bell - Margaret Thatcher's advisor, advertising executive, and supsected removed- who also claimed to have a mole in the TUC. The intelligence services also had either the same or a different informant in Arthur Scargill's inner circle codenamed Silver Fox.
The likes of Roger Windsor were active within the miner's movement and the talks over ending the strike and certainly took on helpful roles. But their other purpose was to gather documents, gossip, and intelligence to be used against the miners in negotiations by both the government and intelligence services who were also tapping people's phones.
A good way to get people to accept something or someone they otherwise wouldn't is to make it/them useful to people who would otherwise by suspicious of it/them.
