Lead shielding

I have made myself a cable tidy which effectively boxes my loudspeaker cables from my 2 aerial cables, and a phono lead from my TV to my amp. The makeup of my room makes this unavoidable.

I designed it with a view to shielding the TV based cables and running a grounding wire to a rod in the garden. I considered the following:
1. run the cables via copper pipes - grounding the said pipe
2. line the respective 'box'/'run' with lead - ground that.

I thought about lead because I saw a roll in my workshop, and understood it to be an effecive shield
Exactly what problem are you trying to solve with your lead shielding?
It would keep Superman from seeing what it is.
Only use lead if you are running a nuclear powered system.
RFI EMI - and Krypton of course - LOL
For a moment, I'll assume that you were actually trying to ask a serious question. Don't waste your time trying to construct a shield for your cables as you described. If you're actually experiencing interference from radio signals, the methods for eliminating that are well known and documented. There's too much to go into here, unless you can tell me the source of the RF interference and frequency of the source signal. Also, what component is being interfered with - your TV, your stereo system, or both? Knowing all the above, the first step would be to determine how the unwanted signal is getting into the component experiencing the interference - could be through the AC power line, antenna line, speaker cables, interconnects. Once that's been determined, then a proper solution can be found. Note that such problems are almost always the fault of the TV or audio equipment not exhibiting the proper rejection of signals that are outside the frequency range that they're designed to deal with. Solutions may involve modifying the audio gear, or installing an appropriate filter (or choke) on the leads that are carrying the signal into the equipment. Tell me more about what's going on and I can give you some specifics.
Look up Mu metal...
Why would you want to introduce a toxic substance into your home?
Joking aside. My amp has a wall socket next to it. Under the wall socket is both my TV aerial, and satellite aerial. my tv is placed between my speakers. My speakers run parallel to the the aerial leads, as well as the tv - to amp phono lead. The shape of my room makes this unavoidable.

I am convinced that this is a recipe for RFI problems entering my audio chain.
The potential is always there for a strong RF signal (from a nearby radio transmitter) to travel on the outside of a shielded cable and couple to other nearby leads. It's never a good idea to bundle a variety of cables into a bundle using velcro or other ties for that reason. If one of those cables happens to be a high impedance phono lead, it can be a real problem. But, without the presence of a strong external RF signal, there is little chance of experiencing RFI from your TV cables. They are low impedance circuits carrying a very weak RF signal and the TV cables are usually 100% shield or multiple shields. What's more of a problem is improperly grounded TV cables that can deliver high voltages from a nearby lightning strike into your equipment. In the USA, satellite and cable TV installers are required to install adequate grounding (tied to your electrical system ground). If that's not done properly, destructive voltages will find their way into your TV and any connected audio and computer equipment.

Getting back to RFI in audio systems, here's a link to an RFI article by a recognized expert in the field: http://audiosystemsgroup.com/RFI-Ham.pdf

The article was written to help amateur radio operators understand the causes and cures of RFI since RFI is a common problem for these people since they have radio transmitters in their homes. Note that in no case is lead shielding even mentioned as the problems are never caused by direct radiation. Using the techniques described in this paper, I've been able to completely eliminate RFI caused by a 1500 watt HF transmitter in the room adjacent to my audio system.

On the other hand, there are those who will believe that even though they are not hearing obvious effects of RFI on their audio system, there are mysterious things happening that have no scientific basis but somehow affect their perceptions. For those folks, I recommend continuing to wrap the head in aluminum foil as the best solution (don't forget the air holes).
Lead is a dense metal with high atomic number, and it can shield all types of harmful radiation x-rays, alpha-rays and gamma rays.
Superman can't see through lead?
Loh, do you hear any difference with or without the shielding?

Lead seems like a reasonable material to try.

I use Mu metal to shield my noise sensitive low level phono gear, works well. It was designed specifically for this purpose in other applications. I think Mu-Metal uses Nickel and Iron mostly, not LEad.

I have read published data on the internet about measured shielding effectiveness of various materials. A google search might be informative.
It would be pointed out mu metal is for absorbing a magnetic field not for shielding anything from RFI. If you're worried about RFI I suggest 3M AB5100S. Lead is one of the worst materials ever foisted upon unsuspecting audiophiles.
Mapman, mu-metal is great for magnetic shielding but it is expensive and difficult to form since after bending it has to be annealed.

Choice of lead is not the best because it is toxic and has high resistivity - 10x higher than aluminum. RFI can get in thru capacitive or electromagnetic coupling. Capacitive coupling can be defeated by shielding but electromagnetic is different story. Non-magnetic copper or aluminum shields don't protect but induced high frequency current travels on the outside of the cable - shield, because of skin effect. For lower frequencies skin effect doesn't work but wavelength become too long for cable to be antenna (Antenna has to be >1/10 of wavelength to be effective). Problem starts when cables are too long.

I would just use good shielded cables and save lead for a rainy radioactive day.