diff --git a/.github/workflows/build-pr.yml b/.github/workflows/build-pr.yml
index db01164a33..cffca9ea3d 100644
--- a/.github/workflows/build-pr.yml
+++ b/.github/workflows/build-pr.yml
@@ -28,6 +28,27 @@ jobs:
       - name: Download eth2network binaries
         run: go test ./... -v -count=1 -run TestEnsureBinariesAreAvail
 
+      # Close specified ports using lsof before testing / local port list compiled from ./integration/constants.go
+      - name: Close Integration Test Ports
+        run: |
+          lowest_port=8000  # Lowest starting port
+          highest_port=58000 # Highest port considering the offset
+          additional_ports=(80 81 99)  # Additional specific ports
+
+          # Find processes listening on ports within the range and kill them
+          for pid in $(lsof -iTCP:$lowest_port-$highest_port -sTCP:LISTEN -t); do
+            echo "Killing process $pid on one of the ports from $lowest_port to $highest_port"
+            kill $pid || true
+          done
+
+          # Close additional specific ports
+          for port in "${additional_ports[@]}"; do
+            for pid in $(lsof -ti TCP:$port); do
+              echo "Killing process $pid on port $port"
+              kill $pid || true
+            done
+          done
+
       - name: Test
         run: go test --failfast -v ./... -count=1 -timeout 5m
 
diff --git a/go/enclave/enclave.go b/go/enclave/enclave.go
index 9385e2c026..2a48d5b03e 100644
--- a/go/enclave/enclave.go
+++ b/go/enclave/enclave.go
@@ -213,7 +213,7 @@ func NewEnclave(
 			blockchain,
 		)
 	} else {
-		service = nodetype.NewValidator(blockProcessor, batchExecutor, registry, rConsumer, chainConfig, config.SequencerID, storage, sigVerifier, logger)
+		service = nodetype.NewValidator(blockProcessor, batchExecutor, registry, rConsumer, chainConfig, config.SequencerID, storage, sigVerifier, mempool, logger)
 	}
 
 	chain := l2chain.NewChain(
@@ -473,9 +473,17 @@ func (e *enclaveImpl) SubmitBatch(extBatch *common.ExtBatch) common.SystemError
 		return responses.ToInternalError(fmt.Errorf("requested SubmitBatch with the enclave stopping"))
 	}
 
-	core.LogMethodDuration(e.logger, measure.NewStopwatch(), "SubmitBatch call completed.", log.BatchHashKey, extBatch.Hash())
+	defer core.LogMethodDuration(e.logger, measure.NewStopwatch(), "SubmitBatch call completed.", log.BatchHashKey, extBatch.Hash())
 
 	e.logger.Info("Received new p2p batch", log.BatchHeightKey, extBatch.Header.Number, log.BatchHashKey, extBatch.Hash(), "l1", extBatch.Header.L1Proof)
+	seqNo := extBatch.Header.SequencerOrderNo.Uint64()
+	if seqNo > common.L2GenesisSeqNo+1 {
+		_, err := e.storage.FetchBatchBySeqNo(seqNo - 1)
+		if err != nil {
+			return responses.ToInternalError(fmt.Errorf("could not find previous batch with seq: %d", seqNo-1))
+		}
+	}
+
 	batch, err := core.ToBatch(extBatch, e.dataEncryptionService, e.dataCompressionService)
 	if err != nil {
 		return responses.ToInternalError(fmt.Errorf("could not convert batch. Cause: %w", err))
diff --git a/go/enclave/nodetype/validator.go b/go/enclave/nodetype/validator.go
index 4997fa3297..0035ceb70f 100644
--- a/go/enclave/nodetype/validator.go
+++ b/go/enclave/nodetype/validator.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"math/big"
 
+	"github.com/ten-protocol/go-ten/go/enclave/txpool"
+
 	"github.com/ethereum/go-ethereum/core/types"
 
 	"github.com/ten-protocol/go-ten/go/common/errutil"
@@ -30,22 +32,14 @@ type obsValidator struct {
 	sequencerID  gethcommon.Address
 	storage      storage.Storage
 	sigValidator *components.SignatureValidator
-	logger       gethlog.Logger
-}
+	mempool      *txpool.TxPool
 
-func NewValidator(
-	consumer components.L1BlockProcessor,
-	batchExecutor components.BatchExecutor,
-	registry components.BatchRegistry,
-	rollupConsumer components.RollupConsumer,
+	logger gethlog.Logger
+}
 
-	chainConfig *params.ChainConfig,
+func NewValidator(consumer components.L1BlockProcessor, batchExecutor components.BatchExecutor, registry components.BatchRegistry, rollupConsumer components.RollupConsumer, chainConfig *params.ChainConfig, sequencerID gethcommon.Address, storage storage.Storage, sigValidator *components.SignatureValidator, mempool *txpool.TxPool, logger gethlog.Logger) ObsValidator {
+	startMempool(registry, mempool)
 
-	sequencerID gethcommon.Address,
-	storage storage.Storage,
-	sigValidator *components.SignatureValidator,
-	logger gethlog.Logger,
-) ObsValidator {
 	return &obsValidator{
 		blockProcessor: consumer,
 		batchExecutor:  batchExecutor,
@@ -55,13 +49,17 @@ func NewValidator(
 		sequencerID:    sequencerID,
 		storage:        storage,
 		sigValidator:   sigValidator,
+		mempool:        mempool,
 		logger:         logger,
 	}
 }
 
-func (val *obsValidator) SubmitTransaction(transaction *common.L2Tx) error {
-	val.logger.Trace(fmt.Sprintf("Transaction %s submitted to validator but there is nothing to do with it.", transaction.Hash().Hex()))
-	return nil
+func (val *obsValidator) SubmitTransaction(tx *common.L2Tx) error {
+	headBatch := val.batchRegistry.HeadBatchSeq()
+	if headBatch == nil || headBatch.Uint64() <= common.L2GenesisSeqNo+1 {
+		return fmt.Errorf("not initialised")
+	}
+	return val.mempool.Validate(tx)
 }
 
 func (val *obsValidator) OnL1Fork(_ *common.ChainFork) error {
@@ -86,6 +84,8 @@ func (val *obsValidator) ExecuteStoredBatches() error {
 		return err
 	}
 
+	startMempool(val.batchRegistry, val.mempool)
+
 	for _, batch := range batches {
 		if batch.IsGenesis() {
 			if err = val.handleGenesis(batch); err != nil {
@@ -155,5 +155,16 @@ func (val *obsValidator) OnL1Block(_ types.Block, _ *components.BlockIngestionTy
 }
 
 func (val *obsValidator) Close() error {
-	return nil
+	return val.mempool.Close()
+}
+
+func startMempool(registry components.BatchRegistry, mempool *txpool.TxPool) {
+	// the mempool can only be started when there are a couple of blocks already processed
+	headBatchSeq := registry.HeadBatchSeq()
+	if !mempool.Running() && headBatchSeq != nil && headBatchSeq.Uint64() > common.L2GenesisSeqNo+1 {
+		err := mempool.Start()
+		if err != nil {
+			panic(fmt.Errorf("could not start mempool: %w", err))
+		}
+	}
 }
diff --git a/go/enclave/txpool/txpool.go b/go/enclave/txpool/txpool.go
index e7ed13f451..37d3141a95 100644
--- a/go/enclave/txpool/txpool.go
+++ b/go/enclave/txpool/txpool.go
@@ -5,6 +5,10 @@ import (
 	"math/big"
 	"strings"
 
+	// unsafe package imported in order to link to a private function in go-ethereum.
+	// This allows us to validate transactions against the tx pool rules.
+	_ "unsafe"
+
 	gethlog "github.com/ethereum/go-ethereum/log"
 	"github.com/ten-protocol/go-ten/go/common/log"
 
@@ -78,6 +82,14 @@ func (t *TxPool) Add(transaction *common.L2Tx) error {
 	return nil
 }
 
+//go:linkname validateTxBasics github.com/ethereum/go-ethereum/core/txpool/legacypool.(*LegacyPool).validateTxBasics
+func validateTxBasics(_ *legacypool.LegacyPool, _ *types.Transaction, _ bool) error
+
+// Validate - run the underlying tx pool validation logic
+func (t *TxPool) Validate(tx *common.L2Tx) error {
+	return validateTxBasics(t.legacyPool, tx, false)
+}
+
 func (t *TxPool) Running() bool {
 	return t.running
 }
diff --git a/integration/constants.go b/integration/constants.go
index 6191b4f932..37449c6dc5 100644
--- a/integration/constants.go
+++ b/integration/constants.go
@@ -8,7 +8,8 @@ const (
 	StartPortSimulationInMem         = 22000
 	StartPortSimulationFullNetwork   = 26000
 	StartPortSmartContractTests      = 30000
-	StartPortContractDeployerTest    = 34000
+	StartPortContractDeployerTest1   = 34000
+	StartPortContractDeployerTest2   = 35000
 	StartPortWalletExtensionUnitTest = 38000
 	StartPortFaucetUnitTest          = 42000
 	StartPortFaucetHTTPUnitTest      = 48000
diff --git a/integration/contractdeployer/contract_deployer_test.go b/integration/contractdeployer/contract_deployer_test.go
index 7fd64f6fa7..5907f99595 100644
--- a/integration/contractdeployer/contract_deployer_test.go
+++ b/integration/contractdeployer/contract_deployer_test.go
@@ -45,7 +45,7 @@ func init() { //nolint:gochecknoinits
 }
 
 func TestCanDeployLayer2ERC20Contract(t *testing.T) {
-	startPort := integration.StartPortContractDeployerTest
+	startPort := integration.StartPortContractDeployerTest1
 	hostWSPort := startPort + integration.DefaultHostRPCWSOffset
 	createObscuroNetwork(t, startPort)
 	// This sleep is required to ensure the initial rollup exists, and thus contract deployer can check its balance.
@@ -81,7 +81,7 @@ func TestCanDeployLayer2ERC20Contract(t *testing.T) {
 }
 
 func TestFaucetSendsFundsOnlyIfNeeded(t *testing.T) {
-	startPort := integration.StartPortContractDeployerTest
+	startPort := integration.StartPortContractDeployerTest2
 	hostWSPort := startPort + integration.DefaultHostRPCWSOffset
 	createObscuroNetwork(t, startPort)
 
diff --git a/integration/eth2network/eth2_network.go b/integration/eth2network/eth2_network.go
index 19bee3d939..33aa0cea89 100644
--- a/integration/eth2network/eth2_network.go
+++ b/integration/eth2network/eth2_network.go
@@ -3,6 +3,7 @@ package eth2network
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -245,7 +246,7 @@ func (n *Impl) Start() error {
 	for i := range n.dataDirs {
 		nodeID := i
 		eg.Go(func() error {
-			return n.waitForNodeUp(nodeID, 30*time.Second)
+			return n.waitForNodeUp(nodeID, time.Minute)
 		})
 	}
 	err = eg.Wait()
@@ -321,22 +322,36 @@ func (n *Impl) Start() error {
 // Stop stops the network
 func (n *Impl) Stop() error {
 	for i := 0; i < len(n.dataDirs); i++ {
-		err := n.gethProcesses[i].Process.Kill()
+		err := kill(n.gethProcesses[i].Process, 0)
 		if err != nil {
 			fmt.Printf("unable to kill geth node - %s\n", err.Error())
-			return err
 		}
-		err = n.prysmBeaconProcesses[i].Process.Kill()
+		err = kill(n.prysmBeaconProcesses[i].Process, 0)
 		if err != nil {
 			fmt.Printf("unable to kill prysm beacon node - %s\n", err.Error())
-			return err
 		}
-		err = n.prysmValidatorProcesses[i].Process.Kill()
+		err = kill(n.prysmValidatorProcesses[i].Process, 0)
 		if err != nil {
 			fmt.Printf("unable to kill prysm validator node - %s\n", err.Error())
-			return err
 		}
 	}
+	// wait a second for the kill signal
+	time.Sleep(time.Second)
+	return nil
+}
+
+const maxTryKill = 5
+
+func kill(p *os.Process, cnt int) error {
+	if killErr := p.Kill(); killErr == nil {
+		return nil
+	} else if !errors.Is(killErr, os.ErrProcessDone) {
+		if cnt >= maxTryKill {
+			return killErr
+		}
+		time.Sleep(time.Second)
+		return kill(p, cnt+1)
+	}
 	return nil
 }
 
diff --git a/integration/eth2network/eth2_network_test.go b/integration/eth2network/eth2_network_test.go
index 15511060cc..4874b44cb0 100644
--- a/integration/eth2network/eth2_network_test.go
+++ b/integration/eth2network/eth2_network_test.go
@@ -65,7 +65,7 @@ func TestStartEth2Network(t *testing.T) {
 		2,
 		2,
 		randomWalletAddrs,
-		time.Minute,
+		2*time.Minute,
 	)
 	// wait until the merge has happened
 	assert.Nil(t, network.Start())
diff --git a/integration/noderunner/noderunner_test.go b/integration/noderunner/noderunner_test.go
index f0b979bfc6..e2e872b034 100644
--- a/integration/noderunner/noderunner_test.go
+++ b/integration/noderunner/noderunner_test.go
@@ -58,7 +58,7 @@ func TestCanStartStandaloneObscuroHostAndEnclave(t *testing.T) {
 		2,
 		2,
 		[]string{hostAddr.String()},
-		time.Minute,
+		2*time.Minute,
 	)
 	defer network.Stop() //nolint: errcheck
 	err = network.Start()
diff --git a/integration/simulation/network/geth_utils.go b/integration/simulation/network/geth_utils.go
index 0af2b329a8..c891c1102c 100644
--- a/integration/simulation/network/geth_utils.go
+++ b/integration/simulation/network/geth_utils.go
@@ -84,7 +84,7 @@ func StartGethNetwork(wallets *params.SimWallets, startPort int, blockDurationSe
 		2,
 		2,
 		walletAddresses,
-		time.Minute,
+		2*time.Minute,
 	)
 
 	err = eth2Network.Start()
diff --git a/integration/smartcontract/smartcontracts_test.go b/integration/smartcontract/smartcontracts_test.go
index f3f8519ff5..151d3691d7 100644
--- a/integration/smartcontract/smartcontracts_test.go
+++ b/integration/smartcontract/smartcontracts_test.go
@@ -71,7 +71,7 @@ func runGethNetwork(t *testing.T) *netInfo {
 		2,
 		2,
 		[]string{workerWallet.Address().String()},
-		time.Minute,
+		2*time.Minute,
 	)
 
 	if err = eth2Network.Start(); err != nil {