True to an extent, but the devil is in the details. The early F1 and F2 Lightnings didn't have the belly and other fuel tanks, so had an endurance of less than an hour, this gave the Lightning a reputation for short range that they've never shaken off.
The Lightning F6 has 5700 litres of internal fuel for its 2 engines, a Mirage IIIE has 3000 litres for its single engine, a Mig 21bis has 2100 litres of fuel for its single engine and an F4C Phantom has 7200 litres for its 2 engines. So a Lightning F6 has 2850 litres of fuel per engine, 5% less than a Mirage IIIE, and like the Mirage flew sorties of about 1 1/2 hours while the Phantom would do 2 1/2 hour sorties.
In practice where the Lightning fell over was external fuel. Mirage III came with 2 drop-tank types, a thin supersonic tank (sometimes with a rocket pod attached to the front) and a fat ferry tank and the centreline and inner wing pylons were plumbed for fuel. The RAAF once put 3 ferry tanks on a Mirage and the tyres popped, so the limit was 2 ferry tanks but they limited speed so the supersonic tanks were used usually for tactical purposes. To reach the Falklands the Argentine Mirages used 2 ferry tanks and struggled with low speed. The Lightning used a pair of over-wing tanks, but these only seem to be used for ferry flights rather than a semi-permanent fixture like the Mirage wing tanks.
I'm doing this from a very old memory, which may be false, but here goes...
It must be over 20 years ago but, I remember reading a book (probably by Bill Gunston) which claimed that English Electric proposed the airframe improvements (i.e. the belly and other fuel tanks plus the wing changes) early enough to be incorporated into the F.1 and F.2 Lightnings as built, but at the time the Air Minstry/RAF wasn't interested.
IIRC he also claimed that English Electric said to him that the Lightning could have been in service earlier (I think it was 2 years) if the Air Ministry/RAF had done certain things differently, but I can't remember what those things were. I do remember the paragraph had the phrases, "to save time" an that in the aviation business "time is money."
However, the earliest primary source I have on official plans for the Lightning is Plan L (Provisional) dated January 1955 covering the period from 31st December 1954 to 31st March 1960. According to that the first 1st Lightning squadron was to be formed in the first quarter of 1959. There was to be one squadron of 16 aircraft 31st March 1959 rising to a front-line force of 80 aircraft in 5 squadrons of 16 on 31st March 1961. Presumably it would have gone on to replace the 208 other short range day fighters (SRDF) in 13 squadrons of 16 aircraft that were projected to be in Fighter Command on 31st March 1960 and the SRDF in the overseas commands.
However, the first Lighting squadron didn't form until June 1960 - 15 months after the first one was planned to be operational. The build up of the Lightning force was slower than planned too:
31st Marcy 1959 - None but:
16 aircraft in one squadron of 16 was planned at January 1955
31st March 1960 - None, but:
80 aircraft in 5 squadrons of 16 were planned at January 1955
36 aircraft in 3 squadrons of 12 were planned at September 1957
31st March 1961 - 24 aircraft in 2 squadrons of 12 (Nos. 56 and 74) but:
84 aircraft in 7 squadrons of 12 were planned at September 1957
31st March 1962 - 36 aircraft in 3 squadrons of 12 (Nos. 56, 74 and 111) but:
156 aircraft in 12 squadrons of 12 or 16 were planned at September 1957
31st March 1963 - 48 aircraft in 4 squadrons of 12 (Nos. 19, 56, 74 and 111) but
156 aircraft in 12 squadrons of 12 or 16 were planned at September 1957
31st March 1964 - 60 aircraft in 5 squadrons of 12 (Nos. 19, 56, 71, 92 and 111)
31st March 1965 - 72 aircraft in 6 squadrons of 12 (Nos. 19, 23, 56, 71, 92 and 111)
60 aircraft in 5 squadrons of 12 were planned in March 1964 so this is an improvement
31st March 1966 - 84 aircraft in 7 squadrons of 12 (Nos. 5, 19, 23, 56, 71, 92 and 111)
84 aircraft in 7 squadrons of 12 were planned in March 1964 so this is spot on
31st March 1967 - 84 aircraft in 7 squadrons of 12 (Nos. 5, 19, 23, 56, 71, 92 and 111)
120 aircraft in 10 squadrons of 12 were planned in March 1964
31st March 1968 - 108 aircraft in 9 squadrons of 12 (Nos. 5, 11, 19, 23, 29, 56, 74, 92 and 111)
120 aircraft in 10 squadrons of 12 were planned in March 1964
Under the March 1964 plan a front-line of 120 Lightnings in 10 squadrons of 12 was to be maintained until 31st March 1975. However, No. 43 Squadron was formed with F-4K Phantoms in 1969 instead of the tenth Lightning squadron. No. 74 Squadron was disbanded in March 1971 reducing the number of Lightning squadrons to 8 and another 2 squadrons converted to F-4M Phantoms in the 1974-75 financial year. Therefore there were actually 6 Lightning squadrons on 31st March 1975 (and 3 Phantom fighter squadrons) instead of 10 (and no Phantom fighter squadrons).
At January 1955 the F.23/49s (it wasn't named the Lightning until October 1958) annual production requirements to 31st March 1960 were:
1 - 1956-57
14 - 1957-58
56 - 1958-59
98 - 1959-60
169 - Total including (15 pre-production aircraft - but 20 pre-production aircraft were built)
However, 25 Lightnings (5 prototypes and 20 pre-production) were on order at January 1955 as follows:
01/04/50 - 2 P.1A and one Static Test Airframe - first flight 04/08/54 and 18/07/55
05/08/53 - 3 P.1B - first flights 04/04/57, 03/09/57 and 03/01/58
26/02/54 - 20 P.1B pre-production aircraft - first flights 03/04/58 to 26/09/59
The first production order for 50 Lightning F Mk 1 aircraft (19 F.1 and 28 F.1A actually built) was placed in November 1956. The first flight was on 03/11/1959.
So it looks as if the first pre-production aircraft flew a year behind schedule (at January 1955). The 16th pre-production aircraft flew on 26/06/59 which is 15 months behind the first production aircraft in the 1959 schedule.
The first flight date comes for the 16th pre production aircraft comes from the UK Serials website. According to that the first production Lightning (XM134) made its first flight on 31/10/1959 and was delivered on 31/03/1960 (the second aircraft wasn't delivered until May 1960). That would make a grand total of 21 Lightnings delivered to 31st March 1960 (excluding the 2 P.1A, 3 P.1B and 3 P.11 prototypes) instead of the 169 projected in January 1955. However, according to the UK Serials site the next 12 aircraft (XM134 to XM146) had flown by 31st March 1960 but had not been delivered.
In September 1957 a grand total of 318 Lightning fighters were required (the number of Lightning trainers had yet to be determined). The 318 Lightning fighters were made up of 50 F.1, 158 F.2 and 110 F.3 aircraft. The 50 F.1 aircraft were on requisition. The 318 aircraft did not include 15 pre-production aircraft which were also on requisition (which increases the total to 333) - except that we know 20 pre-production aircraft were on requisition (which increases the total to 338).
276 of the 318 aircraft were to be delivered to 31st March 1963 as follows:
2 - 1958-59
52 - 1959-60 for a total of 54 by 31st March 1960 instead of the 154 (plus 15 pre-production aircraft planned to be delivered by that date in January 1955)
76 - 1960-61
82 - 1961-62 (78 Mk 2 and 4 Mk 3)
64 - 1962-63
Therefore according to the plan at September 1957 only one production Lightning had been delivered by 31st March 1960 instead of 54.