Lilley was born at Wolverhampton on 10 February 1914. During the Second World War he enlisted into the Coldstream Guards in September 1940 and was one of the founding members of 'L’ Detachment, having joined from No. 8 Commando in September 1941, as one of the Tobruk Four (the others being Pat Riley, Jim Almonds, Jim Blakeney) under officer Lieutenant Jock Lewes, who was killed in December the same year and of whom David Stirling later wrote: "Jock could far more genuinely claim to be the founder of the S.A.S. than I."^[1] Prior to joining 'L' Detachment Sgt Lilley along with Jock Lewes was seconded to Layforce and took part in operations. Subsequently, when Layforce was disbanded Sgt Lilley was attached to 30 Commando and thereafter selected along with Jock Lewis by David Stirling to become part of 'L' Detachment.^[2]

After joining the Coldstream Guards and being posted to North Africa he came to be known as one of the "Tobruk Four" because of the courageous acts he and the other three carried out during the battle for Tobruk.^{[citation needed]} Lilley had served in the SAS since it was first formed in 1941 and won numerous awards for his bravery and service during his time in the British army. These included the Military Medal and the British Empire Medal.

Lilley won the Military Medal in November 1942^[3] for his heroism during a daring raid before continuing to serve the SAS until his discharge in 1958.^{[citation needed]}

He was appointed Regimental Sergeant Major of 21 Special Air Service Regiment in 1950 and was awarded the British Empire Medal for his services in 1952.^[4]

In Special Forces circles, the term boblilley refers to a commando hit-and-run operation.

In May 1942 Stirling wrote a recommendation for an award of the Military Medal:

Lance Sergeant Ernest Thomas Lilley, 'L’ Det S.A.S. Bde (Coldstream Guards). This NCO was cut off and captured by the enemy when returning from a raid on Berka Aerodrome, in May 1942. Although completely unarmed he subsequently managed to surprise and strangle his guard and to return by himself to the RV. He has distinguished himself by great coolness and calmness in other raids.^[5]

In his commendation his GOC Commander Lieutenant Colonel A.C. Newman, called him:

… a legendary soldier greatly deserving the medal for his services to the 21st SAS Regiment. If ever the word for valour could be applied to anyone then it would be most appropriately used to refer to Sgt Lilley.^{[citation needed]}

Lilley was twice^{[citation needed]} Mentioned in Dispatches. The first in January 1944^[6]

On August 1951, Lieutenant Colonel A. C. Newman, VC, commanding officer of the 21st S.A.S. Regiment, wrote:

RSM Lilley was appointed RSM of this unit in September 1950 and for some considerable time before his appointment was carrying out the duties of acting RSM under difficult circumstances in connection with his taking over the appointment. He weathered this period in an extremely resourceful manner.

RSM Lilley has served with SAS troops since they were first formed in 1941. He has a very distinguished war record and was awarded the Military Medal for outstanding bravery in the field, by this outstanding example he has contributed to a very great extent to the reputation earned by SAS troops during the war.

His name is legendary throughout the Regiment and since taking over RSM of 21st SAS Regiment, his qualities of tact, understanding and unswervable loyalty combined with firmness, have been invaluable in a unit combining the SAS role with the previous traditions of the Artists Rifles and containing ranks representative not only of all corps of the Army but of other services and other countries and including a high proportion of ex officers.

He has carried out the difficult job of RSM to a TA unit magnificently and continues to be an example to all ranks. I strongly recommend that he be awarded the BEM for his outstanding services to the Regiment.^[7]

Lilley took part in many operations and missions in North Africa during World War II but perhaps his most acclaimed operation was on the return from a hit and run mission in 1941. Lilley was in a truck with Jock Lewes and David Stirling. Lilley suddenly yelled out for everyone to jump out of the LRDG Chevrolet truck. Lilley had smelled burning and realised that one of the timers pencils in the explosive bombs had activated. Mere seconds after they scrambled out, the truck blew up. Bob Lilley by his quick reaction had saved their lives.^[8]

Lilley was a member of the British Commando team who were parachuted into Norway to destroy the heavy water facility. On completion of the mission he returned from Norway back to the UK by submarine. Lilley later received a certificate of thanks from the King Olav of Norway in December 1945. The letter from King Olav forms part of the Bob Lilley collection.^{[citation needed]}

Post-war, Lilley continued to serve with the SAS, including at least two operational tours in Malaya, his parent unit changing to the South Staffordshire Regiment. Prior to taking his discharge in 1958 he served seven years with 21 Special Air Service Regiment. After his service Lilley retired to Folkestone, Kent and set up a Guest house where many of his old SAS comrades would come and enjoy spending many a happy weekend reminiscing. Lilley died in August 1981 at the age of 67 in Folkestone, Kent. His funeral on 21 August 1981 was attended by Colonel David Stirling and other surviving notables from the SAS originals of 'L' Detachment 1st SAS.^{[citation needed]}

It is reported by a serving officer of 21 SAS that a portrait of Sgt Lilley hangs on the walls of Officer's Mess at the Regimental HQ in Hereford.

The RSM of 21st SAS before Lilley was RSM John Alcock - Croix de Guerre with Silver Star. He was appointed in 1947 and his appointment is recorded in the SAS Newsletter of 1947. Like Lilley he was an ex-Coldstream Guardsman who had fought at Dunkirk.

• Mike Morgan (15 April 2012). Daggers Drawn: Real Heroes of the SAS & SBS. History Press Limited. ISBN 978-0-7524-6606-4.
• Gavin Mortimer (24 November 2011). SAS in World War II: An Illustrated History p.44,54,55,59,73,76,227. Osprey Publishing Company. ISBN 9781849086462.
• Jon E. Lewis, ed. (2011). SAS – The Autobiography "The bravest of the Brave in their own words" p32-p33. Constable & Robinson. ISBN 9781849017206.
• Lorna Almonds-Windmill (19 February 2011). Gentleman Jim: The Wartime Story of a Founder of the SAS and Special Forces. Pen & Sword Books. ISBN 978-1-84884-424-7.
• John Lewes (2007). Jock Lewes: Co-founder of the SAS. First Published: Abe Books Leo Cooper subsequently Pen & Sword Books Limited London. ISBN 978-1844156153.
• Tony Geraghty (August 1980). Who Dares Wins: The Story of the Special Air Service 1950–1980. Arms and Armour Press – London. ISBN 0-85368-457-X.
• Philip Warner (1983). The SAS: The Official History. First Published by William Kimber 1971 subsequently by Sphere Books. ISBN 0-7221-8910-9.
• Virginia Cowles (1958). The Phantom Major: The story of Col David Stirling and the S.A.S. First Published 1958 Collins – London. ISBN 9780006935193.
• "SAS soldier's daring Second World War escape from German camp". Telegraph. 5 December 2012. Retrieved 18 December 2012.
• "BBC News – SAS sale: RSM Bob Lilley's medals sell for £78,000". Bbc.co.uk. 13 December 2012. Retrieved 18 December 2012.