Claims:WE CLAIM: 1. Rolled homogeneous armour (RHA) thick steel plate comprising : of selective C-Mn-Cr-Mo-Ni steel composition in the range of C: 0.20-0.24 %, Mn: 0.98-1.08, P: 0.012 max, S: 0.006 max, Si: 0.27-0.32, Cr: 0.68-0.74, Mo: 0.41-0.45, Ni: 1.62-1.68, Al: 0.025-0.040, B: 0.002-0.0030%, H:2ppm max and the balance is iron having high tensile strength coupled with high hardness ranging from 730 to 875 MPa and 241 to 272 BHN respectively. 2. Rolled homogeneous armour (RHA) thick steel plate as claimed in claim 1 comprising Q & T plates obtained through CC route having yield strength 670-720 MPa, tensile strength 795-820 MPa and % EL 22-23 and that obtained through forging route having 660-800 MPa, 730-875 MPa and 21-24, respectively. 3. Rolled homogeneous armour (RHA) thick steel plate as claimed in anyone of claims 1 or 2 wherein hardness of the Q & T plates obtained through CC route is 257-272 BHN while that Q & T plates obtained through forging route is 241-261 BHN. 4. Rolled homogeneous armour (RHA) thick steel plate as claimed in anyone of claims 1 to 3 having impact Toughness measured from Charpy V-notch impact testing at -40ºC of the Q & T plates produced through CC route is 70-122 Joule while that of Q & T plates produced through forging route is 108-142 Joule. 5. Rolled homogeneous armour (RHA) thick steel plate as claimed in anyone of claims 1 to 4 wherein the plates have a thickness of 120 to 180mm preferably about 150mm. 6. Rolled homogeneous armour (RHA) thick steel plate as claimed in anyone of claims 1 to 5 comprising uniform microstructure consisting of tempered martensite based mechanical properties across the thickness of plate. 7. A process of manufacturing of rolled homogeneous armour (RHA) thick steel plate as claimed in anyone of claims 1 to 6 comprising steps of: C-Mn-Cr-Mo-Ni steel making involving select composition of in the range of C: 0.20-0.24 %, Mn: 0.98-1.08, P: 0.012 max, S: 0.006 max, Si: 0.27-0.32, Cr: 0.68-0.74, Mo: 0.41-0.45, Ni: 1.62-1.68, Al: 0.025-0.040, B: 0.002-0.0030% , H:2ppm max and rest iron ; casting of slabs Hot rolling of slabs following a rolling schedule; following a heat treatment schedule under controlled hardening temperature of 9200C followed by an optimization process to select controlled tempering temperature in the range of 5000C to 6800C such as to obtain desired high tensile strength coupled with high hardness ranging from 730 to 875 MPa and 241 to 272 BHN respectively. 8. A process as claimed in claim 7 wherein the hardening temperature comprise 910-920 0C for 2 min/mm thickness and tempering temperature at 640-6500C for 2.4- 3.0 min/mm thickness. 9. A process as claimed in anyone of claims 7 or 8 following a rolling schedule comprising hot rolling of slab size preferably 250/230x900-970x2100-2330 mm into preferably 150x1000x2000 mm started after soaking the slabs at 1200 to 1300 0C, preferably 1250 0C for 5 hours, after charging the slabs into the furnace, moving from pre-heating zone to heating zone in 1 to 2 hour, preferably ~1.5 hours and from heating to soaking zone in 45 to 75 min, preferably ~1 hour, hot rolling after removal of thick scales using primary de-scaler, with rolling start temperature of the surface of the slab in the range of 1125 to 1175 0C, preferably 1150 °C, cross rolling carried out to achieve the required width with 15-20% of total reduction during each pass wherein the maximum draft of 18-20% of total reduction was provided just before finish pass; and heat-treatment Schedule comprising involving the hardening temperature fixed at 910-920 0C for 2 min/mm thickness and tempering temperature at 640-6500C for 2.4-3.0 min/mm thickness. 10. A process as claimed in anyone of claims 7 to 9 wherein said step of quenching and tempering selectively provide for steel plates with high tensile strength and high toughness properties thick plates which are free from internal defects such cracks, blowholes, etc. 11. A process as claimed in anyone of claims 7 to 10 wherein the steel plates are produced with dimension 150x1000x2000 mm having the yield strength of Q & T plates produced through CC route is 670-720 MPa, tensile strength is 795-820 MPa and % EL is 22-23 while that produced through forging route are 660-800 MPa, 730-875 MPa and 21-24, respectively. 12. A process as claimed in anyone of claims 7 to 11 wherein the said selective steps of manufacture provide steel plates which exhibits Impact Toughness measured from Charpy V-notch impact testing at -40ºC of the Q & T plates produced through CC route is 70-122 Joule while that of Q & T plates produced through forging route is 108-142 Joule. Dated this the 10th day of January, 2018 Anjan Sen Of Anjan Sen & Associates (Applicants Agent) IN/PA-199 , Description:FIELD OF THE INVENTION The present invention is directed to high tensile strength coupled with high toughness in rolled homogeneous armour (RHA) thick steel plates, having C-Mn-Cr-Mo-Ni steel composition comprising various elements in the wt% range of C: 0.20-0.24 %, Mn: 0.98-1.08, P: 0.012 max, S: 0.006 max, Si: 0.27-0.32, Cr: 0.68-0.74, Mo: 0.41-0.45, Ni: 1.62-1.68, Al: 0.025-0.040, B: 0.002-0.0030% and H:2ppm max. In the present invention the chemistry and processing parameters of the product are so adjusted that throughout the thickness uniform microstructure comprising tempered martensite with some amount of bainite may be obtained, which results in achieving almost uniform mechanical properties across the plate thickness of plate. In addition, high levels of both the tensile strength and the impact toughness (CVN) are obtained, enabling the product to be used for various engineering and structural applications. BACKGROUND ART The steels used for general purpose applications are processed and produced through the 'carbon-manganese chemistry' route. This is based on restricting carbon to a low level and alloying with manganese. However, based on the strength and hardness requirements, relatively higher amounts of carbon and manganese contents may be selected for producing steels for high tensile applications. The hot rolled plate may be further quenched and tempered to achieve required strength/hardness and toughness. Medium carbon steels with carbon in the range of 0.25-0.55% have wide ranging engineering applications because mechanical properties in these steels can be varied by varying the carbon content. For special applications such as high temperature etc. alloying with elements such as Ni, Cr, Mo, etc is employed. However, achieving both high strength/hardness and toughness is a challenging job. For this reason, suitable alloy design along with processing including heat-treatment will govern the required mechanical properties whether in as rolled condition or in quenched and tempered condition. Further, achieving high strength/hardness and toughness in thick plates as high as 150 mm is also challenging. In view of this, there has been thus a need in the field of steel making to developing a cost effective composition and process for producing high tensile strength plates with high thickness not less than 150 mm, which is suitable for a variety of engineering applications. US 4572748 A discloses a composition of steel plates comprising 0.03-0.15% by weight of one or more of V, Ti and Nb in addition to the presence of , 0.02-0.50% by weight of Si, 0.4-1.2% by weight of Mn, 0.2-5.0% by weight of Ni, 0.2-1.5% by weight of Cr, 0.2-1.0% by weight of Mo, 0.01-0.10% by weight of acid soluble Al, , 0.015% or less by weight of P, 0.006% or less by weight of S and the balance of iron and inherent impurities.The steel is heated to a temperature above a temperature at which carbo-nitrides of V and Nb and carbides of Ti become complete solid solution state, rolled with total reduction of 40% or more below 950° C., quenched by simultaneous cooling immediately after completion of the rolling from a temperature above (A3 -50)°C. and tempered at a temperature lower than Ac1 temperature. US 6364967 B1 teaches to manufacture steel plates for building structural member with tensile strength of not less than 590 MPa, a yield strength or 0.2% proof strength of not less than 440 MPa and a Charpy impact absorption energy at 0° C. of not less than 47 J was produced. Strength optimization by an alloy that elevates hardenability, texture refinement obtained by fine dispersion of Ti oxides and TiN owing to Ti addition, precipitation strengthening by Cu addition, and formation of a fine bainite texture by temperature-controlled rolling, cooling control and the like enable a high-strength, high-toughness rolled steel shape of high-strength and excellent toughness. The tensile strength and Charpy impact absorption energy at 0C is much lesser than the primary objective region of the present invention. According to the state of the art US 4400225 A, A Cr-Mo steel which is suitable for use as extremely thick plates of 75 mm or greater for pressel vessels of oil refinery, coal liquefaction and coal gasification equipment. The Cr-Mo steel includes 0.09 to 0.17 wt % of carbon, 0.03 to 0.50 wt % of silicon, 0.45 to 0.70 wt % of manganese, 1.80 to 3.40 wt % of chromium, 0.80 to 1.20 wt % of molybdenum, 0.035 to 0.1 wt % of aluminum and 0.0010 to 0.0040 wt % of boron and the balance iron and impurities inevitably mixed in steel-making processes comp C Mn P S Si Cr Mo Ni B Al 0.09-.17 0.45-0.70 0.03-0.05 1.80-3.40 0.8-1.20 0.001-0.004 0.035-0.1 The composition of the present invention is different from the prior art EP 2762594 A1 discloses the finished steel plate with a thickness of 6-25mm has a yield strength of =700MPa, an elongation A50 of=18%, Akv at -60°C of =150J and good cool bending property, appropriately applied to industries of automobiles, engineering machinery and warship hull structures. which contains the following chemical compositions, by weight, C: 0.03-0.06%, Si=0.30%, Mn: 1.0-1.5%, P =0.020%, S=0.010%, Al: 0.02-0.05%, Ti: 0.005-0.025%, N=0.006%, Ca=0.005%, and more than one of Cr=0.75%, Ni=0.40%, Mo=0.30%, other compositions being Ferrum and unavoidable impurities comp C Mn P S Si Cr Mo Ni B Al 0.03-.06 1-1.5 0.02 or less 0.010 or less 0.3 or less 0.75 or less 0.40 or less 0.02-0.05 And also Ti: 0.005-0.025%, N=0.006%, Ca=0.005% US20070181223 A1 The invention relates to a high-strength thick steel plate having a plate thickness of 50 to 80 mm and a tensile strength of 490 to 570 MPa which is able to realize an excellent HAZ toughness even when welding with a heat input of 20 to 100 kJ/mm is conducted and is characterized by containing, by wt %, 0.03-0.14% of C, 0.30% or less of Si, 0.8-2.0% of Mn, 0.02% or less of P, 0.005% or less of S, 0.8-4.0% of Ni, 0.003-0.040% of Nb, 0.001-0.040% of Al, 0.0010-0.0100% of N, and 0.005-0.030% of Ti. and the balance of iron and unavoidable impurities: comp C Mn P S Si Cr Mo Ni B Al 0.03-0.14 0.8-2 .02 or less .005 or less 0.30 or less 0.8-4.0 0.001-0.01 Also contains 0.003-0.040% of Nb 0.0010-0.0100% of N, and 0.005-0.030% of Ti Although the thickness of the steel plates are in the range of 50-80 mm – the tensile strength is 490-570 MPa which is quite below the desired range of tensile strength. EP 3120941 A1: The state of the art disclose a high toughness and high tensile strength, thick steel plate with plate thickness of 100 mm or more, wherein a reduction of area in a center of the plate thickness by tension in a plate thickness direction is 40% or more. Thus, a high tensile strength thick steel plate with excellent strength and toughness in a center of the plate thickness can be obtained with no need for a larger production line, even in the case of producing a high strength thick steel plate for which the addition amount of alloying element needs to be increased. AU2015387626 (A1 Provides a low-yield-ratio high-strength toughness thick steel plate with excellent low-temperature impact toughness, which comprises: 0.05%-0.11% of C, 0.10%-0.40% of Si, 1.60%-2.20% of Mn, S=0.003%, 0.20-0.70% of Cr, 0.20%-0.80% of Mo, 0.02%-0.06% of Nb, 3.60%-5.50% of Ni, 0.01%-0.05% of Ti, 0.01%-0.08% of Al, 0