Mark Steele has absolutely zero idea about RF, electronics. or antennas.
Where is my evidence?
On 2020-09-16 an article was published quoting Mark Steele talking about the LeafNut controller on top of the streetlights in Gateshead, UK. These are nearly identical to the LeafNut product sold in the US. The only difference is the slightly different frequencies used. They use the WiMAX wireless networking protocol to communicate between each streetlight to turn them off and on.
He is reading maximum power and voltage ratings from random components on the circuit board. The amperage from a relay and the voltage from a capacitor. The multiplies these together to get a watage value. Then uses this number to try to suggest that these little controllers can “vaporize people”. This is an absolute farce. It shows how little Mark understands about electronics.
Components have maxiumum rated

He uses this wattage, doesn’t do any antenna analysis and instead asserts that this full electrical power can be transmitted over the air to a person to “vaporize” this person. He does no analysis on the power supply to see the maximum power output it can actually supply to the board.
Because Mark Steele doesn’t understand electronics.
He also doesn’t analyze the radio circuitry to see what the radio’s output is.
Because Mark Steele doesn’t understand radios.
He also doesn’t analyze the gain of the antenna to see how focused the output can be. Where is his EIRP analysis? Don’t worry if you won’t understand EIRP, people that design antennas do, but Mark Steele doesn’t.
Because Mark Steele doesn’t understand antenna design.
The actual the radio in the street lights he is referring to is a 25milliwatt radio, see the design document linked below. That’s 0.025 watts. He claimed 22,500 watts. He is off by a factor of 900,000.
Because Mark Steele refuses to investigate things before he makes wild claims.
Fortunately, the EIRP of the antenna has already been analyzed, see the image below, click on it to get the original document. The analysis is from the same product sold in the US transmitting at 915MHz instead of 868MHz in the UK. All other things are the same. This is the documentation submitted to the US FCC for approval before allowing it to be sold in the US.

The EIRP is 35.4mW. This is higher than the output of 25mW because of the slight gain of the antenna. If you understand EIRP, this is expected. It doesn’t mean the radio can transmit higher than 25mW, it’s an equivalency comparison.

To calculate power exposure use this equation:
S = EIRP/ 4* pi * r^2
The calculated exposure at 20cm is 0.007mW/cm^2. In the UK the max allowed exposure is 20W/m^2 which is 2mW/cm^2.
The exposure is 286 times LOWER than the max allowed exposure in the UK. At 20cm. Note that exposure drops off with the square of the distance.
Human exposure from a device on a street light will be significantly lower because of the distance.
This shows in detail that Mark Steele is wholly unqualified to even have an opinion on RF, electronics, wireless communication networks, or antennas.