Blog Editor’s Note: It’s not always the bad guys who jam GPS. Security forces do so all the time, especially for VIP protection. President Trump is in London this week, so this Notice to Airmen (NOTAM). Notice the 11 nautical mile radius:

NOTAM H2805/19 (NAVW)
N51°30.00 W000°08.00 11nm
Monday, 3 Jun 18:34 to Wednesday, 5 Jun 2019 11:00
Elevation: SFC – 40000
GNSS(GPS) SIGNAL JAMMING. JAMMERS LOCATED WITHIN 2NM RADIUS
POSITION 513013N 0000812W (CENTRAL LONDON). ACTIVITY MAY AFFECT ACFT
WITHIN 11NM (ALL DIRECTIONS) UP TO 40000FT AMSL OR ABOVE MAY ALSO
AFFECT AIRBORNE ELECTRONIC SITUATIONAL AWARENESS DEVICES AND UAS
CONTROL. NOT TO EXCEED 15 MINUTE DURATION. GNSS REC MAY SUFFER
INTERMITTENT/ TOTAL FAILURE, OR GIVE INCORRECT POSITION INFO.
ACTIVITY MAY AFFECT ACFT AND UAS WITHIN 1.5NM (ALL DIRECTIONS)
(433-915MHZ) AND WITHIN 1.1NM (ALL DIRECTIONS)(2.4-5.8GHZ) UP TO
40000FT AMSL OR ABOVE. SOME ELECTRONIC SITUATIONAL AWARENESS DEVICES
AND UAS C2 SYSTEMS MAY SUFFER INTERMITTENT/TOTAL FAILURE OR GIVE
INCORRECT NOTIFICATION. FOR INFO CTC MPS 07785 370911.